Radiative and predissociative lifetimes of the A²Σ⁺ state of OH

Lifetime measurements have been made on the A²Σ⁺ state of OH by the delayed coincidence technique in conjunction with an interrupted rf discharge through water vapor. Lifetimes are reported for rotational states up to K = 29 and K = 20 in the v = 0 and v = 1 vibrational levels respectively and on the unresolved levels of v =2. A predissociation, previously predicted from relative intensity measurements, resulting from a curve crossing by the repulsive 4 Σˉ state, was observed for the rotational states above K = 23 of v = 0, for those above K = 14 of v = 1, and for all those of v = 2. These lifetime data are discussed qualitatively in terms of the electronic-rotational perturbation matrices and the vibrational overlap integrals. The large variation of the transition moment with respect to the internuclear separation and the vibrational-rotational interaction predicted from relative intensities was also observed. For these states (K \u3c 23, v = 0; K \u3c 14, v = 1) the lifetime data are combined with relative intensity measurements to obtain oscillator strengths --Abstract, page iii