MILLIMETER-WAVE SPECTROSCOPY OF CoNO IN THE GROUND $(X^{1}\Sigma)$ STATE
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Date
2004
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Publisher
Ohio State University
Abstract
Infrared spectrum of CoNO has been measured in low temperature Ar matrix and the $\nu_{1}$ and $\nu_{3}$ band origins were reported to be 1761.0 and $620.1 cm^{-1}$ $respectively.^{a}$ Recent DFT calculations suggested that the linear form $(X^{1}\Sigma)$ and bent form $(X^{3}A^{\prime})$ of CoNO have almost the same $energies.^{a}$ In the present study, the pure rotational spectrum of CoNO generated in a supersonic jet expansion by ultraviolet photolysis of $Co(CO)_{3}NO$ was observed in the millimeter-wave region. This is the first observation of the rotationally resolved spectrum of the transition metal nitrosyl in the gas phase. Seven rotational transitions (from $J = 6 - 5$ to $12 - 11$) were measured in the frequency region of $56 - 112$ GHz. Each rotational transition was split into $8-11$ components due to hyperfine interaction of the Co $(I = 7/2)$ nucleus. The spectrum was analyzed to determine molecular constants, including the rotational constant B, centrifugal distortion constant D, nuclear quadrupole interaction constant eQq, and nuclear spin-rotation interaction constant $C_{I}$. From the observed spectral pattern, it is confirmed that CoNO has a linear structure and the electronic ground state is $^{1}\Sigma$. The Co-N bond length was calculated to be 1.588 \AA from the rotational constant, which is by 0.1 \AA shorter than the Co-C bond length of CoCO. Measurement of rotational transitions in the $\nu_{2}$ vibrationally excited state is in progress.
Description
$^{a}$ Mingfei Zhou and Lester Andrews, J. Phys. Chem., A104, 3915 (2000)
Author Institution: Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki
Author Institution: Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki