SUBMILLIMETER WAVE SPECTRA OF NCS
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Date
2003
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Publisher
Ohio State University
Abstract
Rotational spectra of NCS in the excited bending vibrational states have not been analyzed in detail, because of difficulty in analysis due to large Renner - Teller effect and anharmonic interactions. We have extended the observation of the pure rotational spectra of NCS in the $v_{2} = 1$ as well as in the $X^{2}\Pi$ ground state up to $J = 53.5$ in the submillimeter wave region. For the ground state, the analysis was straightforward. The measured transition frequencies were fit to a standard effective Hamiltonian for $^{2}\Pi$ vibronic states, and the improved molecular constants including the higher order centrifugal distortion constants were obtained. The $v_{2} = 1$ vibronic state splits into four vibronic sub-states, $^{2} \Delta_{5/2}, {^{2}} \Delta_{3/2}, \mu^{2} \Sigma$ and $\kappa^{2} \Sigma$. As a first attempt, the $\Delta$ and $\Sigma$ states were fitted separately to effective Hamiltonians. The least square fittings converged by including various effective parameters concerned with the P-type doubling. However, the physical significance of these higher order parameters is not clear. It is found that the spin rotation coupling constant, $\gamma$, and the $\Lambda$-type doubling constants, p, q, are significantly different from those for the ground state. We have attempted to analyze the $\Delta$ and $\Sigma$ states simultaneously by taking into account the perturbations from higher vibrational states. An isotopic species, $NC^{34}S$, in the $X^{2}\Pi_{3/2}$ state has also been measured and $r_{0}$ structure is derived to be $r_{0}(NC) = 1.1805(1)$ {\AA}and $r_{0}(CS)= 1.63212(7) {\AA}$.
Description
$^{a}$NASDA postdoctral fellow
Author Institution: Institute for Astrophysics and Planetary Sciences, Ibaraki University
Author Institution: Institute for Astrophysics and Planetary Sciences, Ibaraki University