Submillimeter-wave spectrum of the AsH₂ radical in the ²B₁ ground electronic state

The pure rotational spectrum of the AsH₂ radical in its ²B₁ ground electronic state was observed for the first time by microwave spectroscopy. The AsH₂ radical was generated in a free-space cell by dc-glow discharge of a mixture of H₂ and O₂ gases over arsenic powder. Fifty-five fine and hyperfine components of six rotational transitions were measured in the frequency region of 304-374 GHz, and were analyzed by least-squares methods. Molecular constants, including the rotational constants, the centrifugal distortion constants, the spin-rotation coupling constant incorporating the centrifugal distortion term, and the hyperfine coupling constants associated with the arsenic and hydrogen nuclei, were precisely determined. The bonding in AsH₂ was discussed on the basis of the hyperfine coupling constants, first determined in the present study.