ANOMALOUS $\Lambda$-DOUBLING IN THE INFRARED SPECTRUM OF THE HYDROXYL RADICAL IN HELIUM NANODROPLETS
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Date
2013
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Ohio State University
Abstract
The $\textit{X}$$^{2}$$\Pi_{3/2}$ hydroxyl (OH) radical has been isolated in superfluid $^{4}$He nanodroplets and probed with infrared laser depletion spectroscopy. From an analysis of the Stark spectrum of the \textit{Q}(3/2) transition, the $\Lambda$-doublet splittings are determined to be 0.198(3) cm$^{-1}$ and 0.369(2) cm$^{-1}$ in the ground and first excited vibrational states, respectively. These splittings are 3.6 and 7.2 times larger than their respective gas phase values. A factor of 1.6 increase in the \textit{Q}(1/2) $\Lambda$-doublet splitting was previously reported for the helium solvated $\textit{X}$$^{2}$$\Pi_{1/2}$ NO radical [K. von Haeften, A. Metzelthin, S. Rudolph, V. Staemmler, and M. Havenith, Phys. Rev. Lett. 95, 215301 (2005)]. A simple model is presented that predicts the observed $\Lambda$-doublet splittings in helium solvated OH and NO. The model assumes a small parity dependence of the rotor's effective moment of inertia and predicts a factor of 3.6 increase in the OH ground state (J=3/2) $\Lambda$-doubling when the \textit{B}$_0^{\textit{e}}$ and \textit{B}$_0^{\textit{f}}$ rotational constants differ by less than one percent.
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Author Institution: Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA