Laser-Induced Fluorescence of BaO

Fluorescence spectra of the $A^1{\mathrm{\Sigma \hspace{0.17em}-\hspace{0.17em}X}}^1\Sigma$ 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 $\text{υ′\hspace{0.17em}=\hspace{0.17em}8}$ , $\text{J′\hspace{0.17em}=\hspace{0.17em}49}$ excited by 488.0 nm and $\text{υ′\hspace{0.17em}=\hspace{0.17em}7}$ , $\text{J′\hspace{0.17em}=\hspace{0.17em}3}$ 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 $\text{υ′\hspace{0.17em}=\hspace{0.17em}7}$ 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 $A^1\Sigma$ state after optical pumping by laser lines. The lifetime of the $A^1\Sigma$ 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 $A^1{\mathrm{\Sigma \hspace{0.17em}-\hspace{0.17em}X}}^1\Sigma$ system of BaO was observed.