Laser-Induced Fluorescence of BaO

Abstract

Fluorescence spectra of the A 1Σ − X 1Σ system of BaO excited by seven visible Ar ion laser lines have been observed over a wavelength region from the exciting lines to beyond 1000 nm. The strongest fluorescence was observed from υ′ = 8, J′ = 49 excited by 488.0 nm and υ′ = 7, J′ = 3 and 7 excited by 496.5 nm. The rotational and vibrational assignments of the various excitation transitions have been made, and rotational and vibrational constants for the lower electronic state were obtained. A rotational perturbation in υ′ = 7 of the upper electronic state was found. Studies have been made, from 0.4 to 40 torr, of the collisional energy transfer to other rotational and vibrational levels of the A 1Σ state after optical pumping by laser lines. The lifetime of the A 1Σ state of BaO was found to be 12 ± 3 × 10−6 sec. The BaO molecules were produced by gas-phase chemical reactions between O2 and Ba vapor in an inert gas at room temperature. A weak chemiluminescence of the A 1Σ − X 1Σ system of BaO was observed.