15min:

P. RASTON, T. LIANG AND G. E. DOUBERLY, Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.

The X ² _3/2 hydroxyl (OH) radical has been isolated in superfluid ⁴He nanodroplets and probed with infrared laser depletion spectroscopy. From an analysis of the Stark spectrum of the Q (3/2) transition, the -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 Q (1/2) -doublet splitting was previously reported for the helium solvated X ² _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 -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) -doubling when the B ₀^ e and B ₀^ f rotational constants differ by less than one percent.