Radiative lifetimes of metastable states of free radicals. I. NF b 1Σ +

Abstract

Metastable excited NF b 1Σ + radicals were generated by means of a pulsed Tesla discharge in a slowly-flowing dilute mixture of NF 3 or N 2F 4 in argon. The excited NF radicals are believed to be generated by energy transfer between Ar 3P 0,2 metastable atoms and NF 3 (or N 2F 4). The decay of NF spontaneous emission near 530 nm, b 1Σ +(υ′=0)-X 3Σ(υ″=0), was used to determine the lifetime of NF b 1Σ +. The results gave a radiative lifetime τ rad equal to (22.6±1.7)×10 −3s (95% confidence limit). The square of the electronic transition moment | R e| 2 was calculated to be (2.1 ± 0.2)×10 −5 D 2 . Rate coefficients ( k M) for quenching of NF b 1Σ + were found to be k NF, = (1.8 ± 0.7) × 10 −12 cm 3 s −1 and k Ar<1 × 10 −17 cm 3 s −1. The method described here is expected to be useful for the study of other excited states whose lifetimes are inthe range 300 μs to 1 s.