An angle-resolved dissociative photoionization study of the c⁴Σ⁻_<i>u</i>state in O⁺₂using the TPEPICO technique

Abstract

We have investigated the angular distributions of O+(4S) ions produced from dissociative photoionization of O+2 c4Σ−u(ν = 0, 1) using the TPEPICO technique, i.e. by measuring the coincidence yield between threshold photoelectrons and photoions. The vibrational levels have distinctly different lifetimes, τν, which diminish their inherent anisotropic photoion angular distribution characterized by a β parameter. We obtain τ1 = 6.0 ± 0.3 × 10−14 s and a lower limit on τ0 of ≈1 × 10−12 s, in broad agreement with other experimental studies using different methods, and find that β = 0.40 ± 0.05, which is significantly at variance with the predicted value of ⩾1.6.