THE LOWEST TRIPLET STATE OF $H_{2}O$

$^{1}$ S. Trajmar, W. Williams and A. Kupperman, J. Chem. Phys. 54, 2274 (1971). $^{2}$ F.W.E. Knoop, H. H. Brongersma and L.J. Oosterhoff, Chem. Phys. Letters 13, 20 (1972).Author Institution: Chemistry Division, Argonne National Laboratory; National Bureau of Standards, Argonne National LaboratoryRecent electron-impact $work^{1,2}$ on $H_{2}O$ shown a broad absorption peak at 4.5 eV which has been attributed to the lowest $^{3}B_{1}$ state of water. Previous ab initio calculations on this state have been at the semiempirical or SCF level and have all given excitation energies greater than 6 eV. We report here a series of SCF and multiconfiguration SCF (MCSCF) calculations on the potential surface of the $^{3}A^{\prime\prime} (^{3}B_{1})$ state. These calculations, which include Rydberg basis functions, indicate that the $^{3}B_{1}$ state is not bound with respect to $OH(^{2}\Pi) + \Pi(^{2}S)$. These results are part of an extensive series of calculations currently underway designed to obtain semi-quantitative information on the potential surfaces of the low-lying states of a number of atmospheric triatomic molecules and ions