ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The diatomic molecule NbS has been observed for the first time by laser-induced fluorescence at low resolution in a supersonic molecular beam following expansion of a CS2/He (1:100) mixture through a laser-produced plasma of niobium atoms. Two band systems have been observed in the visible (400–700 nm); a strong one and a weaker one. The strong one has its origin near 15 670 cm−1 and is shown to belong to the C 4Σ−–X 4Σ− system. The weaker one has its origin likely at 15 215 cm−1 and is attributed to the 2Σ+–X 4Σ−1/2 system. The latter system is observed owing to the 2Σ+(σ1δ2)∼C4Σ−1/2 (δ2σ*1) perturbation induced by the spin–orbit operators. This perturbation has been characterized through vibrational energy shifts, vibronic lifetimes, and analysis of the perturbation matrix elements. This enables direct determination of the large second-order spin–orbit splittings in the C 4Σ− and X 4Σ− states.In the ground state, the splitting which is due to the isoconfigurational 〈2Σ+||Hso||X 4Σ−〉 interaction element has been established to be 63 cm−1 and is independent of the vibrational energy content. In the C state, the spin–orbit splitting arises from two interactions; one due to the isoconfigurational 〈2Σ+||Hso||C 4Σ−〉 interaction and the other to the 〈2Σ−(σ1δ2), (v+1)||Hso||C 4Σ−(δ2σ*1),v〉 interaction. The former interaction splits the C 4Σ−3/2 and C 4Σ−1/2 components by about 63 cm−1, as in the ground X 4Σ− state again independent of the vibrational energy content. The second interaction which becomes negligible at v(C 4Σ−)≥4 shifts the C 4Σ− (v=0,1,2,3) levels to lower wave numbers by 18, 15, 11, and 5 cm−1, respectively. From a Franck–Condon analysis, the electronic part of the molecular matrix elements 〈2Σ+(σ1δ2), v'||Hso||C 4Σ−(δ2σ1*),v‘〉 is estimated to be 57 cm−1. Other molecular parameters such as vibrational frequencies and anharmonicities, radiative lifetimes, Franck–Condon factors, mixing coefficients, and approximate bond lengths are reported and discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.458240
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