SUBMILLIMETER-WAVE SPECTRUM OF THE ASH2 RADICAL IN THE B-2(1) GROUND ELECTRONIC-STATE

The pure rotational spectrum of the AsH2 radical in its B-2(1) ground electronic state was observed for the first time by microwave spectros copy. The AsH2 radical was generated in a free-space cell by dc-glow d ischarge of a mixture of H-2 and O-2 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 c onstants, the centrifugal distortion constants, the spin-rotation coup ling constant incorporating the centrifugal distortion term, and the h yperfine coupling constants associated with the arsenic and hydrogen n uclei, were precisely determined. The bonding in AsH2 was discussed on the basis of the hyperfine coupling constants, first determined in th e present study. (C) 1998 American Institute of Physics. [S0021-9606(9 8)03337-6].