Pulsed discharge jet laser spectroscopy of the stibino (SbH2) free radical: Hyperfine and isotopic structure in the high-resolution electronic spectrum

The Ã2A1-X̃2B1 0-0 bands of the overlapping LIF spectra of 121SbH2 and 123SbH2 have been recorded at high resolution under supersonic expansion conditions. The radicals were made by a pulsed electric discharge through a dilute mixture of SbH3 in high pressure argon at the exit of a pulsed molecular beam valve. The Sb isotopic lines, magnetic hyperfine structure, and large spin-rotation splittings have been assigned in the spectra. The transitions of the two isotopologues were fitted independently, and the rotational constants were used to obtain the following zero-point effective molecular structures: r″ = 1.7203(1) Å, θ″ = 90.370(4)°; r' = 1.6915(4) Å and θ' = 120.80(2)°. The fitted molecular constants have been validated using isotope relations and by comparison with theoretical formulas. The T0 antimony isotope splitting of SbH2 is only 0.0098 cm-1.