TIME-RESOLVED INFRARED DIODE LASER SPECTROSCOPY OF THE $\nu_{1} + \nu_{2} - \nu_{2}$ HOT BAND OF THE FeCO RADICAL PRODUCED BY THE ULTRAVIOLET LASER PHOTOLYSIS OF $Fe(CO)_{5}$
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Date
1999
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Publisher
Ohio State University
Abstract
Time-resolved infrared diode laser spectroscopy was applied to the observation of the $\nu_{1} + \nu_{2} - \nu_{2}$ hot band of the iron carbonyl (FeCO) radical. The FeCO radical was produced by the ArF excimer laser photolysis of iron pentacarbonyl $Fe(CO)_{5}$. Although the FeCO radical has the $^{3}\Sigma^{-}$ electronic ground state, the $\nu_{2}$ bending vibrational excited state has vibronically the $^{3}\Pi$ symmetry, which allows the vibronic interaction with the $^{3}\Pi$ electronic state located very closely, $6400 cm^{-1}$, to the ground electronic $state^{a}$. In the frequency region of $1930-1950 cm^{-1}$, more than 50 R- and P-branch lines were identified which split into triplet $(P = 0, 1$, and 2) due to the spin-spin interaction. Each spin component split further into doublet, as A-type doubling, because of the vibraonic interaction with the nearby $^{3}\Pi$ electronic state. The band origin $\nu_{0} = 1941.54573 (50) cm^{-1}$ was determined as well as the molecular constants for the $\nu_{1} + \nu_{2}$ state, fixing the molecular constants for the $\nu_{2}$ state to those of the millimeter-$wave^{b}$, results. The effective spin-orbit constant $A_{e}f f$ and the A-type doubling constants for the $\nu_{1} + \nu_{2}$ state are much different from those of the $\nu_{2}$ state indicating that the effect of vibronic interaction with the $^{3}\Pi$ electronic state has increased due to the excitation of the $\nu_{1}$ vibration.
Description
$^{a}$ K. Tanaka, M. Shirasaka, and T. Tanaka, J. Chem. Phys., 106, 6820 (1997). $^{b}$ K. Tanaka, M. Nakamura, M. Shirasaka, and T. Tanaka, The 53rd Symposium on Molecular Spectroscopy, Columbus Ohio, (1998) MG16.
Author Institution: Department of Chemistry, Kyushu University
Author Institution: Department of Chemistry, Kyushu University