Measured Radiative Lifetimes and Electronic Quenching Cross Sections of BaO(A 1Σ)

Abstract

Lifetimes of the A ¹Σ state of BaO have been measured for the vibrational levels $\text{v′ = 0}$ 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 $\text{0.275 ± 0.022}$ to $\text{0.389 ± 0.016 μ}\sec$ , with a value of $\text{0.356 ± 0.007 μ}\sec$ for $\text{v′ = 0}$ . 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 ${\text{2.28 × 10}}^{\text{−16}}\mathrm{cm}2$ , 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 $\text{10 ± 2 μ}\sec$ , was observed at high helium pressures from vibrational levels exhibiting strong quenching.