SUBMILLIMETER/THz ROTATIONAL SPECTROSCOPY OF SH+(${X}^{3}{{\rm{\Sigma }}}^{-}$): THE COMPLETEN= $1\leftarrow 0$ TRANSITION

Abstract

The N = 1 0 transition of SH ( in its complete fine structure multiplet (J = 0 1, 2 1, and 1 1) has been measured using submillimeter/THz direct absorption spectroscopy in the frequency range near 346–683 GHz. This work is the first direct laboratory measurement of the J = 0 1 and 1 1 spin components. This molecular ion was created in the gas phase from a mixture of H2S and argon in an AC discharge. Hyperfine components, arising from the nuclear spin of H (I = 1/2), were resolved in every fine structure multiplet. The data have been analyzed using a Hund's case Hamiltonian, resulting in further improvement in the accuracy of the rotational, spin–rotation, spin–spin, and magnetic hyperfine constants for SH From these new data, frequency predictions have been made for the N = 2 1 and 3 2 transitions, with an estimated uncertainty of less than 1 MHz. These data also confirm the recent detection of the two hyperfine components of the N = 1 0, J = 0 1 transition of SH in the Orion Bar, as well as the J = 1 1 component of this molecular ion near 683 GHz toward Sgr B2.