Effect of the Impact Angle on the Kinetic Energy and Angular Distributions of β-Carotene Sputtered by 15 keV Ar₂₀₀₀ Projectiles

Abstract

Molecular dynamics (MD) computer simulations are used to model ejection of particles from β-carotene samples bombarded by 15 keV Ar 2000 . The effect of the incidence angle on the angular and kinetic energy distributions is investigated. It has been found that both of these distributions are sensitive to the variation of the incidence angle, particularly near the normal incidence. For impacts along the surface normal, material ejection is azimuthally symmetric, and a significant emission occurs along the surface normal. The kinetic energy distribution of intact molecules has a maximum near 1 eV and terminates below approximately 2 eV. An increase of the incidence angle breaks the azimuthal symmetry. Most of the intact molecules become ejected in the forward direction. The maximum in the polar angle distribution shifts toward large off-normal angles. In addition, the most probable kinetic energy of ejected molecules is significantly increased. The mechanisms of molecular emission responsible for the observed changes are delineated. The implications of the observed ejection characteristics for the utilization of large gas cluster projectiles in secondary neutral mass spectrometry are discussed.

Argon Cluster Sputtering Reveals Internal Chemical Distribution in Submicron Polymeric Particles

“…In terms of modeling shadowing effects, it permits the rapid calculation of time until sputtering for any volume element simply by calculating the distance between the volume element and the sputtering source that passes through the same, or other, particles. We also assume that redeposition or redistribution does not occur because, although we have some knowledge of ejecta distribution, , the quantities of the material redeposited will be small and not in locations that will affect the analysis presented here.…”