Radiative lifetimes of metastable states of free radicals. II. PF b 1Σ + and CO a 3Π

Abstract

Metastable CO a 3Π and PF b 1Σ + radicals were generated by a pulsed Tesla discharge technique in dilute mixtures of CO 2 and of PF 3 in Ar. For CO a 3Π, ν′ = 0 the averaged radiative lifetime τ rad for the a-X transition. was determined to be (7.9 ± 1.5) ms, and the quenching rate coefficients ( k M cm 3 s −1) obtained were k CO 2 < 3 × 10 −11 and k Ar = (2.3 ± 0.5) × 10 −16, in good agreement with previous determinations by other techniques. For PF b 1Σ +, ν′ = 0 the measurements yielded τ rad = (6.2 ± 0.7) ms, k PF 3 < 5 × 10 −13 and k Ar < 1 × 10 −17. From this value for τ rad a magnitude of (2.2 ± 0.2) × 10 −4 D 2 is calculated for the square of the transition moment, | R e| 2, for PF b 1Σ +-X 3Σ. The transition moment is an order of magnitude larger than that for the corresponding NF transition; reasons for this difference are discussed. The analogous transitions of O 2 and NCl also are considered.