The millimeter/sub-millimeter spectrum of the LiS radical in its (2)Pi(i) ground state

The pure rotational spectrum of LiS (X(2)Pi (i)) has been recorded in the v = 0 and v = 1 states in the region 130-540 GHz using millimeter/sub-millim eter direct absorption methods. This radical was synthesized from lithium v apor and CS2 in a DC discharge. Transitions arising from the two orbit comp onents were measured, both which exhibited lambda-doubling and, for the Ome ga = 1/2 ladder, hyperfine interactions. Rotational, lambda-doubling, and h yperfine parameters have subsequently been determined. These data prove una mbiguously that the ground state of Lis is (2)Pi (i) and suggest that the A (2) Sigma (+) state lies similar to 4300 cm(-1) higher in energy. The bondi ng in this radical appears to be predominantly ionic, (C) 2001 Elsevier Sci ence B.V. All rights reserved.