STIMULATED EMISSION PUMPING (SEP) SPECTROSCOPY APPLIED TO THE METHOXY RADICAL
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Date
2007
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Publisher
Ohio State University
Abstract
Methoxy radical, CH$_3$O is a widely studied and benchmark molecule, both for its spectroscopy and its role in chemical reactions. It possesses a ground $^2$E state which is distorted by the Jahn-Teller interaction and split into $^{2}$E$_{1/2}$ and $^{2}$E$_{3/2}$ components by the spin-orbit interaction. The LIF spectra of the $\tilde{A}^{2}$A$_1$--$\tilde{X}^{2}$E transitions is well-known, but under jet expansion conditions the E$_{1/2}$ component is not observed because it is $\sim$60cm$^{-1}$ higher than E$_{3/2}$ and not populated. A feasible way to study the features of the $\tilde{X}^{2}$E$_{1/2}$ level is to use the Stimulated Emission Pumping (SEP) technique. We have combined our high-resolution laser-induced fluorescence (LIF) spectroscopic ($\Delta\nu\sim$200MHz) with a moderate-resolution laser ($\Delta\nu \sim$0.2cm$^{-1}$). These lasers are controlled by a computer program, which permits both the pump and dump lasers to be fired at specified delays after the photolysis laser producing CH$_3$O. SEP spectra of CH$_3$O were recorded with a resolution of $\approx$300MHz linewidth and measured with a precision $<$100MHz and these data were included in a global data (LIF, SEP, microwave) fitting to determine the parameters of the $\tilde{X}^{2}$E$_{1/2}$ state. The previous assignment of parity for the $^{2}$E$_{1/2}$ state is modified and the value of the spin-orbit splitting revised.
Description
Author Institution: Laser Spectroscopy Facility, Department of Chemistry, The; Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210 (present address: Laboratory of Physical Chemistry, ETH Zurich, Building HCI, Wolfgang-Pauli-Str. 10, 8093; Zurich, Switzerland); Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210; Laser Spectroscopy Facility, Department of Chemistry, The; Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210 (present address: Department of Chemistry, Winston-Salem State University,; Wilveria B. Atkinson Science Bldg, Room 311, Winston-Salem NC 27110); Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210