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A. SHAYESTEH, K. TERESZCHUK AND P. F. BERNATH, Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1, Canada; R. COLIN, Laboratoire de Chimie Physique Moleculaire, Universite Libre de Bruxelles, C.P. 160/09, 50 av. F.D. Roosevelt, 1050 Brussels, Belgium.
We have recorded the first vibration-rotation spectra of gaseous BeH/BeD and BeH2/BeD2 in emission using a furnace-discharge source. The molecules were generated at 1500oC and 333 mA discharge current with beryllium and a mixture of helium and hydrogen or deuterium gases. The recorded spectra contained several emission bands, as well as the absorption of atmospheric H2O and CO2. The highest signal-to-noise ratio for BeH lines was about 350. The vibrational bands v=1-0 to v=4-3 of BeH/BeD were observed in the spectra. The bands were rotationally analyzed, and the spectroscopic constants for v=0 to 4 levels of BeH and BeD, as well as the Dunham constants and the Born-Oppenheimer breakdown constants, were obtained. The antisymmetric stretching mode (
3) of BeH2/BeD2 and several hot bands involving
1,
2 and
3 were found and rotationally analyzed to yield the spectroscopic constants. For BeH and BeD, we determined the equilibrium rotational constants (Be) to be 10.31959(3) cm-1 and 5.68829(2) cm-1, respectively, while the equilibrium vibrational constants (
e) are 2061.416(3) cm-1 and 1529.956(3) cm-1. We also determined Be for BeH2 to be 4.75366(2) cm-1. Using the Be values of BeH and BeH2, the equilibrium Be-H bond distances (Re) were calculated for BeH and BeH2 to be 1.342436(2) Å ~and 1.326407(3) Å, respectively.