ABSTRACT
For fast ions, the majority of energy is transferred in ionizing collisions, resulting in energetic free electrons and the potential energy of residual ions. Energy spectra of secondary electrons ejected by the proton (H+) impact were calculated using the empirical model given by Rudd (1988):
d ( ) d (1 ) {1 exp[ ( )/ ]} i 1 2
S B
F F w w w w vc
σ ε
ε =
+
+ + α − (14.1)
where S = 4πa02Nz2(R/B)2, ε = electron energy, B = binding energy for each orbital, a0 = 0.529 × 10-8 cm, N = electron number in orbital, z = charge of the projectile nucleus, R = 13.6 eV, T = kinetic energy of protons in eVu-1 units, λ = mp/me = 1,836, w = ε/B, ν = (T/λB)1/2, and wc = 4v2 – 2v – R/4B. F1, F2, and α are adjustable ‚tting parameters.
