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Fluorescence spectra of the $A\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma -X\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ system of BaO excited by seven visible Ar-ion laser lines have been observed from the excitation lines to beyond 1000 nm. The experimental arrangement was similar to that previously $described.1$ An ion laser with a prism reflector at one end of the optical resonator was used to obtain single line oscillation. BaO molecules were produced by gas phase chemical reactions between $O2$ and Ba vapor in an inert gas at room temperature. Barium was vaporized in an alumina crucible in cylindrical electric heater. Ba vapor was cooled and carried to the reaction and fluorescence cell by He, $Ar,N2$ gas in excess as compared to the amount of Ba atoms. Rotational lines in the vibrational bands in fluorescence series were well resolved (to $0.08\backslash AA$). Rotational and vibrational assignments of the excitation transitions have been made as shown in Table I. Improved rotational and vibrational constants in the lower electronic state were obtained. $\omega eye$ and $\delta e$ were found to be 0.0045 and $4\times 10-5cm-1$, respectively while other constants are identical to previously measured values.$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ In addition to fluorescence, a weak chemiluminescence of the $A\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma -X\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ system of BaO was observed in this reaction. Studies have been made, from 0.4 to 40 torr, of the collision energy transfer to other rotational and vibration levels of the $A\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ state after optical pumping by laser lines. The transitions from $v\prime =0-12$ in $A\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ state to $v""=0-17$ in ground state were observed. Strong non-thermal distributions of rotational and vibrational populations were observed.[FIGURE]