Measured Radiative Lifetimes and Electronic Quenching Cross Sections of BaO(<i>A</i> 1Σ)

Abstract

Lifetimes of the A 1Σ state of BaO have been measured for the vibrational levels v′ = 0 to 11 from the fluorescence decay excited by a short-pulsed (10 nsec) tunable dye laser. Radiative lifetimes were found to vary with vibrational level from 0.275 ± 0.022 to 0.389 ± 0.016 μsec, with a value of 0.356 ± 0.007 μsec for v′ = 0. Electronic transition moments and absorption oscillator strengths have been calculated from the measured lifetimes. Measured quenching cross sections of BaO (A 1Σ) by helium vary with vibrational level by nearly an order of magnitude from 0.28 to 2.28 × 10−16cm2, suggesting that part of the electronic quenching is through collisional transfer into a perturbing state. Consistent with this model of quenching is the fact that a second fluorescence decay, with a lifetime of 10 ± 2 μsec, was observed at high helium pressures from vibrational levels exhibiting strong quenching.