15min:

A. SHAYESTEH, D. R. T. APPADOO, I. GORDON AND P. F. BERNATH, Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.

We have recorded the vibration-rotation spectra of gaseous MgH and MgH₂ in emission using a furnace-discharge source. The molecules were generated at 650^oC and 333 mA discharge current with magnesium and a mixture of argon and hydrogen gases. The recorded spectra contained several emission bands, as well as the absorption of atmospheric H₂O. The highest signal-to-noise ratio for MgH lines was about 200. Three vibrational bands, v=1-0 to v=3-2, for ²⁴MgH and two vibrational bands for ²⁵MgH and ²⁶MgH were observed in the ^{2 +} ground electronic state. The analysis of the infrared data combined with our previous data on the B'-X electronic transition will lead to an improved potential energy curve for the ground state using a direct-potential-fit approach. In addition to MgH, we found the antisymmetric stretching mode ( ₃) of ²⁴MgH₂ and three hot bands involving ₂ and ₃ in our spectrum. The bands were rotationally analyzed and the spectroscopic constants were determined. The MgH₂ molecule has a linear structure with an R₀ Mg-H bond length of 1.703327(3) Å.