Multiply charged direct recoil spectra from Ar + and Kr + bombarded graphite

Abstract

Measurements of the energy spectra of multiply charged positive and negative carbon ions (C n ± ) recoiling from graphite surface under 100 and 150 keV argon and krypton ion bombardment are presented. With the energy spectrometer set at recoil angle of 79.5°, direct recoil (DR) peaks have been observed with singly as well as multiply charged carbon ions C n ± , where n = 1 to 6. These C n ± ions have been seen recoiling with the characteristic recoil energy E DR = kE 0cos 2 θ DR, where θ DR is the direct recoil angle, k = 4m 1m 2 (m 1 + m 2) 2 , m 1 and E 0 are projectile mass and energy and m 2 is carbon mass. We have observed sharp DR peaks. A collimated projectile beam with divergence ∼ ±0.2° is supplemented with a similar collimation before the energy analyzer to reduce the background of sputtered ions due to scattered projectiles.