NEAR INFRARED BANDS OF $S_{2}$
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Date
1972
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Ohio State University
Abstract
Fragmentary bands observed in the region 6900 - 8100 {\AA} in emission from a microwave discharge through sulphur vapour with helium as a carrier gas, have been shown to be due to $S_{2}$ and to involve transitions from a common initial state $^{3}\Pi_{g}$ to $^{3}\Delta_{u}$ and $^{3}\Sigma_{u}^{+}$ states. The $^{3}\Pi_{g}$ is an inverted state and has a spin splitting of $154 cm^{-1}$. The sub-states, $^{3}\Pi_{2g}$ and $^{3}\Pi_{1g}$, predissociate at $J^{\prime}\geq {34}$ and $J^{\prime}\geq {16}$ respectively while the $^{3}\Pi_{0g}$ state is not observed. Detailed analysis of the rotational structure of the bands shows that the bands at 7506, 7785 and 8083 {\AA} have, in each, six branches $^{P}Q_{12}$, $^{Q}R_{12}$, $^{O}P_{12}$, $^{O}Q_{13}$, $^{P}R_{13}$ and $^{N}P_{13}$ corresponding to transitions from $F_{1}$ levels of $^{3}\Pi_{2g}$ to $F_{2}$ and $F_{3}$ levels of $^{3}\Sigma_{u}^{+}$ state while each of the bands at 7434, 7707 and 7996 {\AA} shows three branches $^{R}Q_{21}$, $^{S}R_{21}$ and $^{Q}P_{21}$ corresponding to transitions from $F_{2}$ levels of $^{3}\Pi_{1g}$ to $F_{1}$ levels of the $^{3}\Sigma_{u}^{+}$ state. The lower state, $^{3}\Sigma_{u}^{+}$, is considered as a transition to Hund’s coupling case (c).
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Author Institution: Bhabha Atomic Research Centre