Publication List of Mario M. Jakas

    1. Particle spectra in multicomponent collsion cascades.

      Mario M. Jakas

      J. Phys. D: Appl. Phys. 38, 1-5 (2005)

    1. Classical Trajectory Monte-Carlo calculations of the electronic stopping cross section for keVs protons and anti-protons impinging on hydrogen atoms.

                        E.R.Custidiano and Mario M. Jakas.

                        Physical Review A 72, 022708-  (2005).

    1. Transport Theory of Sputtering.

      Mario M. Jakas

      Phil. Trans. R. Soc. London A, 139-156 (2004)

    1. Computer-simulation calculations of the electronic stopping of fast, heavy charges by a classical harmonic oscillator.

                         M. M. Jakas, F.J.Pérez  de la Rosa, and E.R. Custidiano.

                        Physical Review A 68, 032903-032909 (2003).

    1. Fluid dynamics calculations of sputtering.

                        Mario M. Jakas                   

                        Nuclear Instruments and Methods in Physics Research B 193, 727-733 (2002).

    1. Fluid dynamics calculation of sputtering from cylindrical thermal spike.

Mario M. Jakas, E. M. Bringa and R.E. Johnson.

Physical Review B 65, 165425- (2002).

    1. Computer-simulation calculations of the electronic stopping of slow, heavy charges by a classical harmonic oscillator.

E.R. Custidiano, F.J.Pérez  de la Rosa and M. M. Jakas.

Physical Review A 66, 052902 (2002).

    1. Computer simulations of the interaction between a heavy charge and a classical harmonic oscillator. 

                        F.J.Pérez  de la Rosa and Mario M. Jakas

                        Radiation Effects and Defects in Solids 157, 289-302 (2002).

    1. Thermal-spike theory of sputtering: The influence of elastic waves in a one dimensional cylindrical spike.

Jakas-M.M.,  E.M. Bringa and R.E. Johnson. 
Physical Review B 62, 824-830 (2000).  Abstract

    1. Spike models for sputtering: effect of the surface and the material stiffness.

Bringa-E.M., Jakas-M.M. and Johnson R.E.
Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B. vol 164-165, April 2000, pages 762-771. Abstract

    1. A Note on thermal spikes and sputtering yields.

Mario M. Jakas
Radiation Effects and Defects in Solids. Vol 152, 157-163 (2000). Abstract

    1. Molecular Dynamics simulations of electronic sputtering.

E.M. Bringa, R.E. Johnson and Jakas-M.M.
Physical Review B60, 15107-15116(1999). Abstract

    1. Solid-state Ozone synthesis by energetic ions.

R.A. Baragiola, C.L. Atteberry, D.A. Bahr and  Jakas-M.M.
Nuclear Instruments and Methods B157, 233-238 (1999). Abstract

    1. The angular dependence of the energy loss for high energy H+-ions transmitted through thin Al films.

M.I. Pascuet, C.J. Aquino, N.E. Capuj, and  Jakas-M.M.
Radiation Effects and Defects in Solids 145,179-190 (1998). Abstract

    1. The production of high-energy electrons during low energy atomic collisions in solids 

      Mario M. Jakas.  

       Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B. vol.115, no.1-4; July 1996; p.255-60. Abstract

    1. Increasing efficiency of ion-solid Monte Carlo simulations by using stratified sampling.

      Mario M. Jakas

Radiation-Effects-and-Defects-in-Solids. vol.141, no.1-4; 1997; p.23-36.  Abstract

    1. The influence of multiple scattering and Coulomb repulsion on the transmission of H2+ through solid targets.

Capuj-NE and Jakas-MM.

Nuclear Instrum.and Methods in Physics research, Section B 115 , 146 (1996).  Abstract

    1. Trapping of a classical electron between two heavy scattering centers.

Mario M. Jakas
Physical-Review-A-. vol.52, no.1; July 1995; p.866-9. Abstract

    1. Monte Carlo calculations of the energy loss for H2+ molecular ions transmitted through thin C and Al foils.

Jakas-MM; Capuj-NE.  Physical-Review-A-. vol.52, no.1; July 1995; p.439-44. Abstract

    1. Wake effects on the energy loss as a function of the scattering angle for thin-film-transmitted H2+ ions.

Jakas-MM and Capuj-NE.
Physical-Review-A-. vol.54, no.6; Dec. 1996; p.5031-6.  Abstract

    1. Monte Carlo calculation of the energy-loss spectra for fast H2+ molecular ions transmitted through thin foils.

Jakas-MM and Capuj-NE. 

Journal-of-Physics:-Condensed-Matter. vol.7, no.24; 12 June 1995; p.4593-601. Abstract

    1. Orbiting of free, classical electrons in the field of two slowly approaching charges. 

      Jakas-MM; Hernandez-Cabrera-AJ and Aceituno-P.

Modern-Physics-Letters-B. vol.9, no.5; 28 Feb. 1995; p.299-305 Abstract

    1. Increasing efficiency in Monte Carlo simulations by a killing-and-splitting strategy.

      Jakas-MM and Capuj-NE.

Physica-A. vol.215, no.1-2; 15 April 1995; p.51-60.  Abstract

    1. Wake forces and the transmission yield of H2+ through thin carbon foils.

Jakas-M.M. and Capuj-NE.
Physical-Review-A-. vol.51, no.3; March 1995; p.2277-80. Abstract

    1. Calculation of energetic H2+-transmission yield using an efficient Monte Carlo algorithm.

Jakas-MM and Capuj-NE.

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B. vol.B93, no.1; July 1994; p.14-20.  Abstract

    1. Wake effects on the transmission of fast H2+-ions through thin carbon foils.

Mario M. Jakas

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B. vol.B93, no.1; July 1994; p.11-13.  Abstract

    1. Computer simulation of growth during molecular-beam epitaxy of metal-on-metal surfaces.

Mario M. Jakas
Vacuum. vol.44, no.3-4; March-April 1993; p.337-9.  Abstract

    1. Wake effects on the center of mass of dissociated molecules traversing thin solid films.

       Mario M. Jakas

      Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B. vol.B69, no.1; June 1992; p.142-5. Abstract

    1. Slow-ion-induced single excitations in an electron gas.

                        J. Calera-Rubio,  A. Gras-Martí,  N.R. Arista,  Mario M. Jakas, S. Sroubek  and G. Falcone.

                        Radiation Effects and Defects in Solids, 117, 173- (1991).

    1. Electronic excitations by slow ions in metals.

Calera-Rubio-J; Gras-Marti-A; Arista-NR; Jakas-MM; Sroubek-Z; Falcone-G.

Surface-Science. vol.251-252; July 1991; p.136-9.  Abstract

    1. On liquid-film thickness measurements with the atomic-force microscope.

Forcada-ML; Jakas-MM and Gras-Marti-A.
Journal-of-Chemical-Physics. vol.95, no.1; 1 July 1991; p.706-8. Abstract

    1. Inhomogeneity effects  on  the  energy  loss  spectra  of  protons transmitted  through  thin  solid  films.

                         N.R. Capuj, and  Mario M. Jakas.

                        Ion-Solid Interactions, Eds. Gras-Martí, F.Flores,  N.R.Arista,  Plenum (1990). 

    1. Corrections to vicinage-effect data for molecular ions due to foil inhomogeneities.

Jakas-MM and Capuj-NE.
Physical-Review-A-. vol.40, no.12; 15 Dec. 1989; p.7369-72. Abstract

    1. Scaling for the angular variation of the energy loss of ions induced by foil inhomogeneities.

Jakas-MM and Capuj-NE.
Nuclear-Instruments-&-Methods-in-Physics-Research, Section-B.  vol.B36, no.4; April 1989; p.491-3. Abstract

    1. Thin-film inhomogeneities studied by energy-loss measurements using ion beams.

      Capuj-NE; Eckardt-JC; Lantschner-GH; Arista-NR and Jakas-MM.

      Physical-Review-A. vol.39, no.3; 1 Feb. 1989; p.1049-52. Abstract

    1. Thin film inhomogeneity characterization  by  ion-beam technique.

                        N.E. Capuj, J.C. Eckardt, G.H. Lantschner, N.R. Arista  and  Mario M. Jakas.

                        Proc. Plasma-Surface Interaction and Processing of Materials, Alicante, Spain (1988).  

    1.  Theoretical analysis of the influence of foil  inhomogeneities  on the angular variation of the  energy-loss.

                        N.E. Capuj  and  Mario M. Jakas.

                        Proc. Plasma-Surface Interaction and Processing of Materials, Alicante, Spain (1988).

    1. Variation of peak energy for energy loss with angle of observation.

Lantschner-GH; Eckardt-JC; Jakas-MM; Capuj-NE and Ascolani-H.

Physical-Review-A. vol.36, no.10; 15 Nov. 1987; p.4667-71.  Abstract

    1. Noble-gas ion sputtering yield of gold and copper: dependence on the energy and angle of incidence of the projectiles.

Oliva-Florio-A; Baragiola-RA; Jakas-MM; Alonso-EV and Ferron-J.

Physical-Review-B-. vol.35, no.5; 15 Feb. 1987; p.2198-204. Abstract

    1. Analysis of secondary-electron emission in beam-foil experiments with molecular ions.

      Arista-NR; Jakas-MM; Lantschner-GH and Eckardt-JC.

Physical-Review-A-. vol.34, no.6; Dec. 1986; p.5112-4. Abstract

    1. Simulation of the atomic collision cascade.

Harrison-DE-Jr; Jakas-MM.
Radiation-Effects. vol.99, no.1-4; 1986; p.153-69.  Abstract

    1. Inelastic energy losses in cascades and atom ejection.

Harrison-DE-Jr and Jakas-MM.
Nuclear-Instruments-&-Methods-in-Physics-Research, Section B . vol.B15, no.1-6; April 1986; p.25-8. Abstract

    1. The computer simulation of ion induced atomic collision cascades.

Webb-RP; Harrison-DE-Jr; and Jakas-MM.

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B. vol.B15, no.1-6; April 1986; p.1-7.  Abstract

    1. A comparison between multiple interaction computer simulations and the linear theory of sputtering.

Jakas-MM and Harrison-DE-Jr.
Nuclear-Instruments-&-Methods-in-Physics-Research, Section B . vol.B14, no.4-6; April 1986; p.535-41. Abstract

    1. Many-body effects in atomic-collision cascades.

Jakas-MM and Harrison-DE-Jr.
Physical-Review-Letters. vol.55, no.17; 21 Oct. 1985; p.1782-5. Abstract

    1. Dependence of atom ejection on electronic energy loss.

Jakas-MM and Harrison-DE-Jr.
Physical-Review-B-. vol.32, no.5; 1 Sept. 1985; p.2752-60.  Abstract

    1. Computer studies of the reflection of 30 keV N2+ ions from a (010)Cu surface.

       Jakas-MM and Harrison-DE-Jr.

Surface-Science. vol.149, no.2-3; Jan. 1985; p.500-16.  Abstract

    1. Influence of electronic energy losses on atom ejection processes.

Jakas-MM and Harrison-DE-Jr.
Physical-Review-B-. vol.30, no.6; 15 Sept. 1984; p.3573-4. Abstract

    1. The correlation between inelastic energy loss and scattering angle in transmission experiments.

Eckardt-JC; Lantschner-GH; Jakas-MM andPonce-VH.

Nuclear-Instruments-&-Methods-in-Physics-Research, Section B . vol.230, no.1-3; March 1984; p.168-72.  Abstract

    1. Anomalous enhanced backscattering of fast light ions from amorphous solid targets.

       Jakas-MM and Ponce-VH.

Journal-of-Physics-D-(Applied-Physics). vol.17, no.6; 14 June 1984; p.1301-14. Abstract

    1. Study on the angular dependence of the average energy loss for ions in solids.

       Jakas-MM; Lantschner-GH; Eckardt-JC and Ponce-VH.

Physical-Review-A-. vol.29, no.4; April 1984; p.1838-43. Abstract

    1. Variational calculation of the angular width of the multiple scattering distribution in foil transmission.

Jakas-MM and Biersack-JP.
Zeitschrift-fur-Physik-A-(Atoms-and-Nuclei). vol.315, no.1; 1984; p.29-33. Abstract

    1. Angular dependence of stopping power.

Jakas-MM; Lantschner-GH; Eckardt-JC and Ponce-VH.
Physica-status-solidi-B. vol.117, no.2; 1 June 1983; p.K131-4.  Abstract

    1. Energy loss for electronically elastic atom-molecule collisions in the keV energy range.

      Mario M. Jakas

Physical-Review-A-. vol.25, no.3; March 1982; p.1782-5. Abstract

    1. Z1-dependence of the ion-induced electron emission  from aluminum.

                        E.V.  Alonso,  R.A.  Baragiola,  J.  Ferrón,  M.M.  Jakas  and  A.R. Oliva-Florio.

                        Physical Review.  B 22, 80 (1981). 

    1. Energy reflection by back-scattering and sputtering: total yields and angular distribution 

      Jakas-MM and Williams-MMR.

Journal-of-Physics-D-(Applied-Physics). vol.13, no.7; 14 July 1980; p.1169-80  Abstract

    1. Explanation for the 180 degrees Rutherford backscattering anomaly in solids 

      Jakas-MM and Baragiola-RA.

Physical-Review-Letters. vol.44, no.6; 11 Feb. 1980; p.424-6  Abstract

    1. Energy dependence of the molecular effect in sputtering.

Oliva-Florio-AR; Alonso-EV; Baragiola-RA; Ferron-J and Jakas-MM.

Radiation-Effects-Letters. vol.50, no.1; 1979; p.3-7  Abstract

    1. Fluctuation in the spatial distribution of energy deposited by atomic particles. 

      Mario M. Jakas

Physics-Letters-A. vol.72A, no.6; 6 Aug. 1979; p.423-6.  Abstract


  1. Spike models for sputtering: effect of the surface and the material stiffness.


Bringa-E.M., Jakas-M.M. and Johnson R.E. Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B vol. 164-165, April 2000, pages 762-771.

Abstract


 

  1. Thermal-spike theory of stputtering revisited I: The influence of  elastic waves in a one-dimension cylindrical spike.


Jakas-M.M. and E.M. Bringa. Submitted to Physical Review B.

Abstract
 
 


A Note on thermal spikes and sputtering yields.

Jakas-M.M. Radiation Effects and Defects in Solids. Vol 152, 157-163 (2000).

Abstract


Molecular Dynamics simulations of electronic sputtering. E.M. Bringa, R.E. Johnson and

Jakas-M.M. Physical Review B60, 15107-15116(1999).

Abstract


Solid-state Ozone synthesis by energetic ions.

R.A. Baragiola, C.L. Atteberry, D.A. Bahr and  Jakas-M.M. Nuclear Instriments and Methods B157, 233-238 (1999).

 

Abstract

The angular dependence of the energy loss for high energy H+-ions transmitted through thin Al films.

M.I. Pascuet, C.J. Aquino, N.E. Capuj,  Jakas-M.M..  Radiation Effects and Defects in Solids 145,179-190 (1998).

Abstract

The production of high-energy electrons during low energy atomic collisions in solids.

Jakas-MM.

Nuclear-Instruments-&-Methods-in-Physics-Research, Section-B . vol.115, no.1-4; July 1996; p.255-60.
 

Abstract


The acceleration of electrons during low-energy atomic collisions in solids is studied. It is shown that a classical, high energy electron can be "trapped" in a sequence of head-on collisions with the ion and the target atom. Then, due to the Fermi acceleration mechanism the trapped electron may absorb energy from the center-of-mass motion up to a maximum value, above which such a sequence becomes unstable. A quantum study of the same process indicates that virtual states appear higher in the continuum of the quasi-molecule formed by the nuclei in the colliding pair, which can be used by the  electron to increase its energy during the incoming part of the collision.

The influence of multiple scattering and Coulomb repulsion on the transmission of H2+ through solid targets.

Capuj-NE; Jakas-MM.

Nuclear-Instruments-&-Methods-in-Physics-Research, Section-B . vol.115, no.1-4; July 1996; p.146-51

Abstract
The transmission yield of H2+ ions through solid targets decreases rapidly with dwell time in the foil. This is basically due to the occurrence of three mechanisms: screened Coulomb repulsion, multiple scattering and the wake forces. Using Monte Carlo simulations, we studied the relative importance of these processes in the transmission yield by switching them "on" and "off" alternatively. It was found that for small dwell times the yield drops mainly as a result of the Coulomb repulsion between the nuclei. At larger dwell times multiple scattering by target atoms becomes the dominant mechanism; whereas the wake forces become important at bombarding energies smaller than 150 keV/amu.


Increasing efficiency of ion-solid Monte Carlo simulations by using stratified sampling.

Jakas-MM.

Radiation-Effects-and-Defects-in-Solids. vol.141, no.1-4; 1997; p.23-36

Astract
A procedure that increases the efficiency in Monte Carlo simulations is presented. It is based on a technique known as stratified sampling, according to which random numbers are sampled so as to increase the number of predetermined results. This technique was applied to the study of high-energy carbon ions backscattered from a Si target. Despite the fact that backscattering yields are fairly small, the energy spectra can be calculated within reasonable computing times. The possibility of including this procedure into a general-purpose ion-solid simulator is also discussed.


Trapping of a classical electron between two heavy scattering centers.

Jakas-MM.

Physical-Review-A-. vol.52, no.1; July 1995; p.866-9.

Abstract
This paper shows that a classical electron may get trapped within the field of two atomic nuclei even though it is free, i.e., the total energy of the electron is greater than that at large distances from the attractive centers. The consequences of this phenomenon for the emission of high-energy electrons during slow-atom bombardment of solids are discussed.


Monte Carlo calculations of the energy loss for H2+ molecular ions transmitted through thin C and Al foils.

Jakas-MM; Capuj-NE.

Physical-Review-A-. vol.52, no.1; July 1995; p.439-44

Abstract
We calculate the mean energy loss of H2+ molecular ions transmitted through carbon and aluminum foils as a function of the bombarding energy. Our results are in good agreement with available experimental data. Furthermore, inhomogeneities containing the foil are found to be essential in the energy-loss measurement of transmitted molecular ions.


Wake effects on the energy loss as a function of the scattering angle for thin-film-transmitted H2+ ions

Jakas-MM; Capuj-NE

Physical-Review-A-. vol.54, no.6; Dec. 1996; p.5031-6

Abstract
We calculated the mean energy loss as a function of the exit angle for 100 and 400 keV/amu H2+ ions transmitted through thin carbon foils. The results showed that at 100 keV the energy loss exhibited a maximum in the forward direction as opposed to that of protons, which had a minimum at zero degree ejection angle. Our studies demonstrate that such a difference stems from the wake or polarization forces acting upon the trailing ion in the cluster.


Monte Carlo calculation of the energy-loss spectra for fast H2+ molecular ions transmitted through thin foils.

Jakas-MM; Capuj-NE.

Journal-of-Physics:-Condensed-Matter. vol.7, no.24; 12 June 1995; p.4593-601.

Abstract
We report calculations of the energy-loss spectra for 25-300 keV/amu H2+ ions transmitted through carbon and aluminium foils. At 25 keV/amu the mean energy-loss of transmitted H2+ ions is approximately 15% smaller than that of two protons at the same velocity, whereas at 300 keV/amu it becomes 10% greater. When compared to those of two uncorrelated protons, the width of the energy-loss distribution appears to increase with a decrease of the bombarding energy, becoming 3-5 times larger at 25 keV/amu for molecules transmitted through aluminium and carbon foils, respectively.


Orbiting of free, classical electrons in the field of two slowly approaching charges.

Jakas-MM; Hernandez-Cabrera-AJ; Aceituno-P.

Modern-Physics-Letters-B. vol.9, no.5; 28 Feb. 1995; p.299-305

Abstract
The motion of a free, classical, spinless electron in the field of two nuclei during low velocity atomic collisions is investigated. It is found that if one neglects the bremmstrahlung and interactions with other electrons, a free electron can orbit around the two nuclei with a surprisingly high stability. A maximum energy, however, appears above which such an orbiting becomes unstable. The connection between these findings and the acceleration of electrons by means of the Fermi shuttle effect is also discussed.


Increasing efficiency in Monte Carlo simulations by a killing-and-splitting strategy.

Jakas-MM; Capuj-NE.

Physica-A. vol.215, no.1-2; 15 April 1995; p.51-60.

Abstract
We have derived a procedure which increases the efficiency of Monte Carlo simulations. It aims at special cases in ion-solid simulations where the probability of success becomes particularly small. Efficiency results from killing and splitting trajectories according to a certain importance figure assigned to a number of sites along the ion trajectory. A much simple case, however, is studied which, on the one hand, retains the essentials of ion-solid simulations, without, on the other hand, going into unnecessary complications.


Wake forces and the transmission yield of H2+ through thin carbon foils.

Jakas-MM; Capuj-NE.

Physical-Review-A-. vol.51, no.3; March 1995; p.2277-80.

Abstract
The transmission of 0.05-1.0 MeV/amu H2+ molecular ions has been calculated as a function of dwell time in carbon foils. The results indicate that wake forces may have a manifest influence upon the transmission yields. Experimental results, however, are lacking within the range of dwell time and bombarding energy where wake effects are expected to become noticeable.


Calculation of energetic H2+-transmission yield using an efficient Monte Carlo algorithm.

Jakas-MM; Capuj-NE.

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B-(Beam-Interactions-with-Materials-and-Atoms). vol.B93, no.1; July 1994; p.14-20.

Abstract
The transmission yield of 0.1-1.0 MeV/amu H2+ molecular ions as a function of dwell-time ( tau ) in thin carbon foils have been calculated by Monte Carlo (MC) simulations. As transmission yields drop rapidly with increasing dwell-time, the simulations are speeded up by using a technique known as killing-and-splitting (KS). This technique enables us to simulate, for the first time, the transmission of molecules over the entire range of dwell-time where experimental results are available, i.e., 0< tau <30 fs. A detailed description of the KS-method and comparisons of calculations with previous experiments are offered.


Wake effects on the transmission of fast H2+-ions through thin carbon foils.

Jakas-MM

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B-(Beam-Interactions-with-Materials-and-Atoms). vol.B93, no.1; July 1994; p.11-13.

Abstract
According to Monte Carlo calculations the transmission of 0.1-1.0 MeV/amu H2+ molecular ions through thin carbon foils show a particularly high sensitivity upon the presence of wake forces. Our results also disagree with previous evidences pointing towards a nearly universal curve for the transmission yield as a function of dwell-time in the foil. Existing experiments however do not actually allow us to check for the validity of our calculations.


Computer simulation of growth during molecular-beam epitaxy of metal-on-metal surfaces.

Jakas-MM.

Vacuum. vol.44, no.3-4; March-April 1993; p.337-9.

Abstract
By using Monte Carlo simulations we analyse the development of topographic features (on the atomic scale) during the growth of an initially flat surface. The role of deposition rate and several parameters characterizing the motion of atoms on the surface is investigated. Particular attention is paid to identify mechanisms which may explain the origin of the layer-by-layer growth as reported in previous experiments.


Wake effects on the center of mass of dissociated molecules traversing thin solid films.

Jakas-MM.

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B-(Beam-Interactions-with-Materials-and-Atoms). vol.B69, no.1; June 1992; p.142-5.

Abstract
Calculations are presented showing that wake forces can be observed on the angular distribution of the center of mass (COM) of dissociated fragments in Coulomb explosion experiments. The author's results indicate that wake forces produce a broadening in the angular distribution of the COM which may be comparable to that of multiple scattering. Results contained in this paper aim at new applications of Coulomb explosion techniques, especially for experiments equipped with x-z position-sensitive detectors.


Electron excitations by slow ions in metals.

Calera-Rubio-J; Gras-Marti-A; Arista-NR; Jakas-MM; Sroubek-Z; Falcone-G.

Surface-Science. vol.251-252; July 1991; p.136-9.

Abstract
The energy and angular distribution of electrons excited by slow charged particles penetrating an electron gas, is analyzed using a representation of the particle by a general self-consistent potential. The number of excited electrons per unit path-length is also calculated. Oscillations with the nuclear charge of the ion, Z, are obtained for the spectra of electron excitations and the total excitation rate. These Z oscillations have the same origin as those found, both theoretically and experimentally, for the stopping power of low-velocity ions. The connection of electron excitation spectra with ion
slowing down and with experiments on secondary electron emission is discussed.


On liquid-film thickness measurements with the atomic-force microscope.

Forcada-ML; Jakas-MM; Gras-Marti-A

Journal-of-Chemical-Physics. vol.95, no.1; 1 July 1991; p.706-8.

Abstract
The authors provide a theoretical description of some measurements were the thicknesses of solid-supported thin lubricant films are measured using the atomic-force microscope (Mate et al., J. Chem. Phys. 90, 7550 (1989)). In their model, the differences observed between the thicknesses measured with the force microscope and ellipsometric thicknesses are explained by the appearance of an instability in the liquid film. Their calculations also predict the dependence of these differences on the thickness of the film.


Corrections to vicinage-effect data for molecular ions due to foil inhomogeneities

Jakas-MM; Capuj-NE.

Physical-Review-A-. vol.40, no.12; 15 Dec. 1989; p.7369-72.

Abstract
Calculations are presented showing the influence of foil inhomogeneities upon the mean energy loss of molecular ions transmitted through thin films. They indicate that, due to the strong dependence of the transmission of molecular ions on thickness, previous measurements of the stopping of such ions at low bombarding energies can be affected by thickness variations of the foil.


Scaling for the angular variation of the energy loss of ions induced by foil inhomogeneities.

Jakas-MM; Capuj-NE.

Nuclear-Instruments-&-Methods-in-Physics-Research, Section-B . vol.B36, no.4; April 1989; p.491-3.

Abstract
Analytical calculations have been made in order to assess the influence of foil inhomogeneity upon the angular variation of the mean energy loss of atomic projectiles, and to calculate the path-length as a function of the exit angle of ions transmitted through thin, inhomogeneous foils. By introducing reduced values of angle and thickness and assuming that the degree of inhomogeneity amounts to a small perturbation, a scaling law was obtained which allows one to obtain a general solution independent of particle and target species, energy, and inhomogeneity.


Thin-film inhomogeneities studied by energy-loss measurements using ion beams.

Capuj-NE; Eckardt-JC; Lantschner-GH; Arista-NR; Jakas-MM.

Physical-Review-A-. vol.39, no.3; 1 Feb. 1989; p.1049-52.

Abstract
A method to evaluate thin-film thickness inhomogeneities is presented. It is based on the measurements of the first two moments of the energy-loss distributions of swift ions traversing thin foils at two different beam incidence angles. The authors apply the method to a set of thin ( approximately 200-AA) aluminum foils, resolving thickness fluctuations of the order of 10%.


Variation of peak energy for energy loss with angle of observation.

Lantschner-GH; Eckardt-JC; Jakas-MM; Capuj-NE; Ascolani-H.

Physical-Review-A-. vol.36, no.10; 15 Nov. 1987; p.4667-71.

Abstract
The energy loss for protons on Al, Cu, and Ag thin foils around the maximum of the stopping have been measured at two different exit angles. The bombardment energy E/sub max/ where such a maximum occurs is found to depend on the angle of observation, E/sub max/ being greater when the detector is positioned off beam than when measured downstream in the beam direction. These results are discussed in terms of a varying participation of different electrons in the target. The effect of foil inhomogeneities on E/sub max/ is also evaluated.


Noble-gas ion sputtering yield of gold and copper: dependence on the energy and angle of incidence of the projectiles.

Oliva-Florio-A; Baragiola-RA; Jakas-MM; Alonso-EV; Ferron-J.

Physical-Review-B-. vol.35, no.5; 15 Feb. 1987; p.2198-204.

Abstract
The authors have measured the sputtering yield of Au and Cu targets as a function of energy and the angle of incidence of noble-gas projectiles in the energy range 2-50 keV. The experimental results were compared with the analytical theory of sputtering and with computer simulations. Their study indicates that the linear-cascade model is applicable only asymptotically for low nuclear stopping powers.


Analysis of secondary-electron emission in beam-foil experiments with molecular ions.

Arista-NR; Jakas-MM; Lantschner-GH; Eckardt-JC.

Physical-Review-A-. vol.34, no.6; Dec. 1986; p.5112-4.

Abstract
The authors analyze the possibility of large oscillatory wake effects in secondary-electron emission induced by molecular ions, which were proposed in previous interpretations of results derived from beam-foil experiments. They show that theoretical expectations are in disagreement with the description of such oscillatory effects in terms of wake phenomena. Their analysis of various experimental evidences suggests a different origin for the effect. They propose a simple explanation for the molecular effect in secondary-electron emission, which is based on previous knowledge of electron emission from solid targets, and of molecular effects in the energy loss of ion clusters in solid foils.


Simulation of the atomic collision cascade

Harrison-DE-Jr; Jakas-MM

Radiation-Effects. vol.99, no.1-4; 1986; p.153-69

Abstract
Molecular dynamics computer simulations can be used to evaluate pre-existing theoretical concepts, or used directly as a research tool, simulations can directly investigate natural phenomena. The TRIM program, a binary-collision simulation of atomic collision cascades, is a well-known example of the first usage. The authors compare and contrast TRIM results with computations from a multiple-interaction cascade simulation program, QDYN. QDYN is described in detail; then some issues of potential function development for simulation use are introduced, followed by some examples of QDYN based research. Two current simulation based research topics are presented in greater detail. One is a study of very low energy cascades, where directed bonds and chemical effects are important. The other is the influence of electronic processes on cascade development. Characteristics of atoms ejected from the surface are emphasised. Both topics have potential applications in the si! mulation of atomic collision cascades in insulators. These investigations emphasise the possibility that direct comparisons between simulations of collision cascades in metals, semiconductors, and insulators can help to solve outstanding research problems in both fields.


Inelastic energy losses in cascades and atom ejection

Harrison-DE-Jr; Jakas-MM

Nuclear-Instruments-&-Methods-in-Physics-Research, Section B . vol.B15, no.1-6; April 1986; p.25-8

Abstract
Recent molecular dynamics simulation studies demonstrated the important role that electronic stopping plays in the sputtering of metals when the loss rate is proportional to the velocity. Inelastic energy losses by the ions and energetic recoil atoms have relatively little effect, but losses by low energy atoms, late in the cascade, significantly reduce the ejected atom yield. The simulation results are consistent with recently obtained analytic results. Here ejected atom yield ratios and energy and ejection time distributions are compared, with and without inelastic losses, for two simulation programs: TRIM.SP, a binary collision model and QDYN, a multiple interaction model. The results differ little within a given model, and the differences between models are well understood.


The computer simulation of ion induced atomic collision cascades

Webb-RP; Harrison-DE-Jr; Jakas-MM.

Nuclear-Instruments-&-Methods-in-Physics-Research,-Section-B-(Beam-Interactions-with-Materials-and-Atoms). vol.B15, no.1-6; April 1986; p.1-7

Abstract
The use of computer simulation to understand the physics of atomic collision phenomenon has escalated in recent years. Even with this proliferation of simulation codes the majority of programs fall into two categories-the event store and the time step models. These models are discussed, and a hybrid formed from the two is described. The best uses of each model is indicated and some examples given. The event store simulations give an accurate method of evaluating range data and the time step models conveniently give information on cascade propagation and nonlinear behaviour.

A comparison between multiple interaction computer simulations and the linear theory of sputtering.

Jakas-MM; Harrison-DE-Jr.

Nuclear-Instruments-&-Methods-in-Physics-Research, Section B . vol.B14, no.4-6; April 1986; p.535-41.

Abstract
A multiple interaction simulation and a binary collision simulation modified to mimic the analytic linear theory of sputtering, have been used to study the sputtering of metal targets by ions with keV energies. Detailed comparisons between the two models disclose fundamental differences in the behaviour of collision cascades at energies below 1.0 keV. The binary collision models' failure to include multiple interactions, i.e. many-body collision effects, is a significant shortcoming, which can lead to serious misunderstandings and misinterpretations of the basic physical processes which are commonly identified as 'nonlinear' sputtering.


Many-body effects in atomic-collision cascades.

Jakas-MM; Harrison-DE-Jr.

Physical-Review-Letters. vol.55, no.17; 21 Oct. 1985; p.1782-5

Abstract
Molecular-dynamics simulations have been used to identify two cooperative atom-ejection mechanisms which increase sputtering yield. Their effects are analogous to the 'thermal spike', 'shock wave', and 'reduced binding energy' sputtering mechanisms. They are examples of nonlinear, many-body effects in cascades which go beyond collisions between randomly moving particles.


Dependence of atom ejection on electronic energy loss

Jakas-MM; Harrison-DE-Jr

Physical-Review-B-. vol.32, no.5; 1 Sept. 1985; p.2752-60

Abstract
The authors extend previous theoretical models to emphasize the influence of electronic energy losses upon the ejection of atoms by bombarding ions. This sensitivity of the sputtering yield to inelastic energy losses was first observed in computer simulations of sputtering. The theoretical analysis supports the simulation-derived conclusion that the total yield is much more sensitive to electronic energy losses by the atoms than to electronic energy losses of the bombarding ions, even when the ion is much lighter than the target atoms.


Computer studies of the reflection of 30 keV N/sub 2//sup +/ ions from a (010)Cu surface

Jakas-MM; Harrison-DE-Jr

Surface-Science. vol.149, no.2-3; Jan. 1985; p.500-16

Abstract
The reflection of 30 keV N/sub 2//sup +/ molecular ions from a Cu(010) surface has been studied using molecular dynamics multiple interaction simulations. The model is used to investigate the trajectories leading to the reflection of undissociated N/sub 2//sup +/ ions. A theoretical analysis of the reflection of diatomic molecules is also given, which provides proper insight into the process as well as a useful guide to the simulations. In contrast to previous theories, correlations in the motion of molecule's nuclei were found to play an important role on the reflection of bound clusters.


Influence of electronic energy losses on atom ejection processes

Jakas-MM; Harrison-DE-Jr

Physical-Review-B-. vol.30, no.6; 15 Sept. 1984; p.3573-4

Abstract
Two independent computer simulations models establish that when ions bombard solid targets, electronic energy losses by atoms within the collision cascade have greater influence on the ejected atom yield than the ion's electronic losses. This conclusion is independent of the ion's mass or energy, or the mass ratio.


The correlation between inelastic energy loss and scattering angle in transmission experiments

Eckardt-JC; Lantschner-GH; Jakas-MM; Ponce-VH

Nuclear-Instruments-&-Methods-in-Physics-Research, Section B . vol.230, no.1-3; March 1984; p.168-72

Abstract
The authors measure the energy loss as a function of the emergence angle, and the angular spread as a function of the energy loss for 50-200 keV H/sup +/ and He/sup +/ on 410 AA C and 170 AA Al foils. A strong dependence of the angular spread on the energy loss has been observed, as well as an angular dependence of the energy loss far beyond that predicted by path length enlargement and nuclear stopping power. Theoretical expressions for the previous magnitudes were obtained on the basis of a multiple scattering formalism and a single collision energy loss-scattering angle function Q( theta ). In addition, a procedure is presented to retrieve this Q-function from the experimental data.


Anomalous enhanced backscattering of fast light ions from amorphous solid targets

Jakas-MM; Ponce-VH

Journal-of-Physics-D-(Applied-Physics). vol.17, no.6; 14 June 1984; p.1301-14

Abstract
The anomalous enhanced backscattering of fast light ions from heavy amorphous solid targets is studied within the formalism of transport theory. The angle distribution of emerging ions is obtained by a variational procedure, where the correlation in the collisions on the incoming and outgoing paths is treated as a perturbation. When using a power potential for the ion-target interaction this distribution can be expressed in terms of reduced variables for the emerging angle and backscattering depth, and the dependence on the collision energy and atom species appears only on the scale factors. The observation of the enhancement in the distribution of backscattered ions will depend on the value of these scale factors as compared with the experimental resolutions.


Study on the angular dependence of the average energy loss for ions in solids

Jakas-MM; Lantschner-GH; Eckardt-JC; Ponce-VH

Physical-Review-A-. vol.29, no.4; April 1984; p.1838-43

Abstract
By using the transport theory, the authors have derived a general expression which connects Delta E( theta ), the average energy loss measured at different theta emergence angles, and Q( theta ), the average elastic and inelastic energy loss in a single scattering as a function of the scattering angle theta , for ions transmitted through thin films. In this way, the effect of multiple scattering of the angular dependence of the energy loss is properly taken into account. By means of this procedure the average energy-loss function Q is retrieved from experimental Delta E( theta ) data, as the authors show for the cases of 50-200-keV H/sup +/ on C and Al foils.


Variational calculation of the angular width of the multiple scattering distribution in foil transmission

Jakas-MM; Biersack-JP

Zeitschrift-fur-Physik-A-(Atoms-and-Nuclei). vol.315, no.1; 1984; p.29-33.

Abstract
A simple formula is derived for calculating the angular width of multiple scattering distributions for atomic particles traversing thin foils. The universal result is obtained by applying the variational method on standard multiple scattering theory. This procedure can be carried through in a straight-forward way, thus saving lengthy series expansions and Fourier transforms. In the case of power cross sections exact analytical expressions can be obtained. A remarkably good agreement is found between this calculation and previous theories, as well as with results from computer simulations.


Angular dependence of stopping power

Jakas-MM; Lantschner-GH; Eckardt-JC; Ponce-VH

Physica-Status-Solidi-B. vol.117, no.2; 1 June 1983; p.K131-4

Abstract
In a recent publication, Iferov and Zhukova (1982) reported measurements of the stopping power as a function of the observation angle for 100 to 400 keV protons transmitted through gold films. According to them, Q( theta ), the average inelastic energy loss in a single scattering having a scattering angle theta , is related with Delta E( theta ), the stopping power measured within the angle theta according to the expression Q( theta )= Delta E( theta )- Delta E(0)- Delta E/sub n/( theta )-( theta /sup 2//4) Delta E, where Delta E/sub n/( theta ) is the nuclear energy loss corresponding to the scattering angle theta and the last term in the expression represents the increase of the observed energy loss when going from theta =0 to theta not=0 due to enlargement in the ion path length, and Delta E is the average energy loss for such a beam-foil experiment. The authors aim to show that the expression is an oversimplification and therefore not correct.


Energy loss for electronically elastic atom-molecule collisions in the keV energy range

Jakas-MM

Physical-Review-A-. vol.25, no.3; March 1982; p.1782-5

Abstract
An analytical expression is obtained for the average energy loss of atomic projectiles scattered by homonuclear diatomic molecules in the absence of electronic excitations.


Z/sub 1/ dependence of ion-induced electron emission from aluminum

Alonso-EV; Baragiola-RA; Ferron-J; Jakas-MM; Oliva-Florio-A

Physical-Review-B-. vol.22, no.1; 1 July 1980; p.80-7

Abstract
The authors have measured the electron emission yields gamma of clean aluminum under bombardment with H+, H2+, D+, D2+, He+, B+, C+, N+, N2+, O+, O2+, F+, Ne+, S+, Cl+, Ar+, Kr+, and Xe+ in the energy range 1.2-50 keV. The clean surfaces were prepared by in situ evaporation of high-purity Al under ultra-high-vacuum conditions. It is found that kinetic electron emission yields gamma /sub k/, obtained after subtracting from the measured gamma a contribution due to potential emission, are roughly proportional to the electronic stopping powers, for projectiles lighter than Al. For heavier projectiles there is a sizable contribution to electron emission from collisions involving rapidly recoiling target atoms, which increases with the mass of the projectile, and which dominates the threshold and near-threshold behavior of kinetic emiss! ion. The results, together with recently reported data on Auger electron emission from ion-bombarded Al show that the mechanism proposed by Parilis and Kishinevskii of inner-shell excitation and subsequent Auger decay is negligible for light ions and probably small for heavy ions on Al and in the authors' energy range. The authors thus conclude that kinetic electron emission under bombardment by low-energy ions results mainly from the escape of excited valence electrons.


Energy reflection by back-scattering and sputtering: total yields and angular distribution

Jakas-MM; Williams-MMR

Journal-of-Physics-D-(Applied-Physics). vol.13, no.7; 14 July 1980; p.1169-80

Abstract
The energy reflection coefficient-total yields and angular distributions-have been calculated by solving the transport equation for the average kinetic energy flux. The energy flux transported by projectiles and by recoils were evaluated separately, thus the back-scattering and sputtering contributions to the reflected energy were obtained. The authors considered an infinite medium of stopping material and neglected the electronic energy loss as well as crystalline effects. The introduction of a power scattering law leads to the reduction of the integral equation for the energy flux to an algebraic system of equations for the spatial moments. An analytical treatment to evaluate the energy flux carried by the projectiles is also included. Good agreement was found between the authors theory and experiment, in particular with recently reported angular distributions of the reflected energy. A special aspect of this work lies in the use of a synthetic kernel to rep! resent the anisotropy of scattering in the laboratory system of co-ordinates.


Explanation for the 180 degrees Rutherford backscattering anomaly in solids

Jakas-MM; Baragiola-RA

Physical-Review-Letters. vol.44, no.6; 11 Feb. 1980; p.424-6

Abstract
An explanation is given for the unusual enhancement in the Rutherford backscattering yield at 180 degrees found by Pronko et al. (1979). It involves a nonstochastic dependence between inward and outward trajectories of backscattering projectiles. Results are presented of Monte Carlo simulations in random solids which show excellent agreement with experiment without need of considering electronic disturbances induced by the projectiles.


Energy dependence of the molecular effect in sputtering

Oliva-Florio-AR; Alonso-EV; Baragiola-RA; Ferron-J; Jakas-MM

Radiation-Effects-Letters. vol.50, no.1; 1979; p.3-7

Abstract
Reports measurements of sputtering yields of Au for Xe/sup +/ and Xe/sub 2//sup +/ impact in the energy range 1-50 keV. It was found that non-linear effects exist well outside the range predicted in a recent thermal spike model (Sigmund, 1974).


Fluctuation in the spatial distribution of energy deposited by atomic particles.

Jakas-MM.

Physics-Letters-A. vol.72A, no.6; 6 Aug. 1979; p.423-6.

Abstract
The standard deviation distribution corresponding to the spatial distribution of energy deposited in the slowing down of atomic particles in solids is calculated. Large fluctuations are found that agree well with Monte Carlo simulations for fluctuations in the deposited energy and sputtering yields.