The Electronic Spectrum and Molecular Geometry of the Jet-Cooled Stibino (SbH2) Free Radical
Abstract
The jet-cooled stibino (SbH2) free radical has been detected for the first time. This highly reactive species was produced in an electric discharge through a precursor mixture of stibine (SbH3) diluted in high pressure argon. Stibine was synthesized by the low-temperature reduction of SbCl3 with LiAlH4 and stored and handled at -85 oC to avoid decomposition. Low-resolution LIF scans revealed a single band of SbH2 with complex rotational structure in the 514.9 - 511.0 nm region. We find that the fluorescence lifetimes of the rotational transitions in this band are very short, of the order of 50-75 ns, suggesting an upper state dissociative process. The spectrum is assigned to the \tilde{A}2A1 - \tilde{X}2B1 electronic transition by analogy with the known spectra of NH2, PH2 and AsH2 and in accord with a recent high level ab initio study. Emission spectra obtained after laser excitation of single rotational lines in the 0-0 band show a ground state bending frequency of approx. 820 \wn, consistent with theoretical predictions. The rotationally resolved spectrum of the 0-0 band, which spans some 150 \wn, was recorded at a resolution of 0.08 \wn and analyzed in detail. The spectrum is complicated by large spin splittings and Sb hyperfine effects. The molecular constants were used to determine the geometry of SbH2 in both states.
- Publication:
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74th International Symposium on Molecular Spectroscopy
- Pub Date:
- June 2019
- DOI:
- 10.15278/isms.2019.TD02
- Bibcode:
- 2019isms.confETD02S
- Keywords:
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- Radicals