title: Nonadiabatic dynamics in energetic negative fluorine ions scattering from a Si(100) surface.
abstract: The dependence of the negative-ion fractions on incident energy and angle is reported for 8.5-22.5 keV F(-) ions scattered from a Si(100) surface at a fixed scattering angle of 38°. The negative-ion fraction increases monotonically with incident velocity for specular scattering. In particular, the variation of the fraction with incident angle is bell shaped for a given incident energy. We interpret this variation using the incident-velocity effect at short distances where the yield of negative ions depends on the number of initial neutrals. It strongly indicates that at short distances, a dynamical equilibrium population is never achieved. This nonadiabatic feature is supported by simple calculations using modified rate equations.
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Shunli
authors.initials: S
authors.lastname: Qiu
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Xiong
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Jianjie
authors.initials: J
authors.lastname: Lu
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Pinyang
authors.initials: P
authors.lastname: Liu
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Ding
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Cui
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Guo
authors.affiliation: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
authors.forename: Ximeng
authors.initials: X
authors.lastname: Chen