THE MILLIMETER/SUBMILLIMETER SPECTRUM OF METHYLPHOSPHINE, CH$_3$PH$_2$ (\ {X}$^1$A)

Author Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721; Department of Chemistry, University of Kentucky, Lexington, KY 40506; Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ 85721The millimeter/submillimeter spectrum of methylphosphine, CH$_3$PH$_2$ (\~{X}$^{1}$A), has been measured using direct absorption techniques. Previously, only the microwave spectrum had been recorded. This molecule was created by the reaction of gas-phase phosphorus and methane or Si(CH$_3$)$_4$ in the presence of argon carrier gas and an AC glow discharge. Several transitions have been recorded in the range 280 - 422 GHz in both the v = 0 and v = 1 states each with multiple asymmetry components ranging from K$_a$ = 0 to 16. Several of the K$_a$ components in the v = 0 state show A/E splittings, while others appear collapsed. The v = 1 state has multiple K$_a$ components with A/E splittings and is currently being analyzed. The data for the v = 0 state has been fit with an asymmetric top Hamiltonian, including internal rotation interactions, and the spectroscopic constants have been determined. Methylphosphine is the third row analog of methylamine, a known interstellar molecule, and could be a potential interstellar species