Survival probability of an excited sputtered Al atom in the 4s2S1/2 state from a polycrystalline Al surface as a function of surface-oxygen coverage

The survival coefficient has been determined for an excited Al atom in the 4s2S1/2 state formed in sputtering of a polycrystalline Al surface under Ar+ bombardment as a function of the steady-state surface-oxygen coverage θ∞(t→∞) of the target surface. Doppler-line profiles were measured for the resonance line of Al (396.152 nm, 4s2S1/2→3p2P03/2) for a projectile energy of 40 keV. The line profiles were analyzed with the Thompson–Sigmund energy distribution multiplied by the survival probability. It was found that the survival coefficient has a maximum around θ∞∼0.1 and becomes smaller when θ∞ goes to 0 i.e. the quantum-tunneling probability has a maximum at surface-oxygen coverage of θ∞∼0.1 for the present case. Mean velocity component of sputtered excited Al atoms parallel to the target surface was presented as a function of θ∞.