Electron promotion and electronic friction in atomic collision cascades

We present a computer simulation model for the space- and time-resolved calculation of electronic excitation energy densities in atomic collision cascades. The model treats electronic friction as well as electron promotion as a source term of electronic energy that is carried away from the original point of excitation according to a nonlinear diffusion equation. While the frictional source is treated within the Lindhard model of electronic stopping, electron promotion is described using diabatic correlation curves derived from ab initio molecular orbital energy level calculations in combination with the Landau–Zener curve crossing model. Results calculated for two selected collision cascades show that the electron promotion mechanism may contribute significantly to the excitation energy density in the cascade volume, giving rise to distinct peaks of the local electron temperature at the surface. This contribution is essentially restricted to the first 100 fs after the projectile impact and may therefore be of significance for either external or internal kinetic electron emission. At later times, where the bombardment-induced particle kinetics lead to the sputter ejection of material from the surface, the excitation is shown to be primarily governed by electronic friction. This finding is important in light of excitation and ionization probabilities of sputtered particles.

[1]  V. Buss,et al.  The role of electronic friction of low-energy recoils in atomic collision cascades , 2007 .

[2]  E. Pehlke,et al.  Kinetic excitation of solids : The concept of electronic friction , 2006 .

[3]  J. Yarmoff,et al.  Ion formation and kinetic electron emission during the impact of slow atomic metal particles on metal surfaces , 2006 .

[4]  R. Baragiola,et al.  Kinetic electron excitation in the interaction of slow Kr+ ions with Al surfaces , 2005 .

[5]  A. Wucher,et al.  Low-energy electronic excitation in atomic collision cascades: A nonlinear transport model , 2005 .

[6]  R. Baragiola.  Invited review: Some challenging unsolved problems in atomic collisions in solids , 2005 .

[7]  H. Winter,et al.  Near-threshold emission of electrons during grazing scattering of keV Ne atoms from an Al(111) surface , 2005 .

[8]  Z. Šroubek,et al.  Electronic excitation in atomic collision cascades , 2005 .

[9]  F. Šroubek,et al.  Computer simulation of low-energy electronic excitations in atomic collision cascades , 2004 .

[10]  D. Diesing,et al.  Kinetic electron excitation in atomic collision cascades. , 2004, Physical review letters.

[11]  H. Winter,et al.  Classical model of kinetic electron emission near threshold induced by impact of atomic projectiles on a free-electron gas metal , 2003 .

[12]  B. Garrison,et al.  Theoretical study of mechanisms responsible for emission of highly excited metal atoms , 2003 .

[13]  Rafd A. BaragioIa.  Principles and mechanisms of ion induced electron emission , 2002 .

[14]  Reinhart Heinrich,et al.  Self-sputtering of silver by mono- and polyatomic projectiles: A molecular dynamics investigation , 2001 .

[15]  Jijun Zhao,et al.  Tight-binding study of structural and electronic properties of silver clusters , 2001 .

[16]  J. Fine,et al.  High-energy electron emission from ion-bombarded surfaces of Ga, Ge, In and Sn , 1997 .

[17]  R. Souda,et al.  Electron promotion in low-energy rare-gas ion scattering from solid surfaces , 1995 .

[18]  T. Tombrello,et al.  An instantaneous inelastic energy loss algorithm for use in molecular dynamics simulations , 1995 .

[19]  Fine,et al.  Electronic excitations produced by deep-level promotion during atomic collisions in solids. , 1995, Physical review. B, Condensed matter.

[20]  T. Tombrello,et al.  Molecular dynamics simulations of inelastic energy loss effects in sputtering II , 1994 .

[21]  B. Garrison,et al.  Electronic distortion in keV particle bombardment , 1994 .

[22]  C. L. Kelchner,et al.  Construction and evaluation of embedding functions , 1994 .

[23]  Dan N. Bernardo,et al.  keV particle bombardment of solids: molecular dynamics simulations and beyond , 1994 .

[24]  J. Rabalais.  Low energy ion-surface interactions , 1994 .

[25]  J. Fine,et al.  Amolecular dynamics simulation of collisional excitation mechanisms in Al , 1993 .

[26]  Z. Sˇroubek.  Formation of ions in sputtering , 1989 .

[27]  D. Lo.  Molecular dynamics simulation of sputtering , 1989 .

[28]  K. Groeneveld,et al.  Ion induced electron ejection from solids , 1983 .

[29]  P. Joyes.  Theoretical models in secondary ionic emission , 1973 .

[30]  Walter A. Harrison,et al.  Solid state theory , 1970 .

[31]  W. Lichten,et al.  Interpretation of Ar + -Ar Collisions at 50 KeV , 1965 .

[32]  J. Lindhard,et al.  ENERGY DISSIPATION BY IONS IN THE kev REGION , 1961 .