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 (Cn ±) 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 Cn ±, where n = 1 to 6. These Cn ± ions have been seen recoiling with the characteristic recoil energy EDR = kE0cos2 θDR, where θDR is the direct recoil angle, k = 4m 1 m 2 (m 1 + m 2 ) 2 , m1 and E0 are projectile mass and energy and m2 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.