: |
: |
|---|
MOTOKI NAKASHIMA, SEIKI IKEDA, TOSHIHIDE HIKIDA, KEIICHI TANAKA AND TAKEHIKO TANAKA, Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki, Higashiku, Fukuoka, 812-8581 JAPAN.
Rovibrational transitions of the
3 band (C-O anti-symmetric stretch) of the Co(CO)2 radical were observed in the frequency region of 1944 - 1964 cm-1. The Co(CO)2 radical was produced by the 248 nm excimer laser photolysis and the transient absorption signal was detected by time-resolved infrared diode laser spectroscopy.
More than 160 absorption lines were assigned to the
3 fundamental band. The
3 band consists of two series of spectral lines spaced approximately by four times the rotational constant, due to the spin statistics of identical C and O nuclei, and the electronic ground state was confirmed to be X2
_\textrmg. Molecular constants including the band origin
0, rotational constant, and centrifugal distortion constant were derived from the observed transitions. Hot bands originating from the
7 and 2
7 vibrational excited states, where
7 refers to the C-Co-C bending mode, were also observed. Because of the rovibronic interaction, each of the observed lines for the
3 +
7 \gets
7 and
3 + 2
7 \gets 2
7 hot bands was split into two and three components, respectively.
Ab initio calculation in BP86/6-311+G* level suggests that the Co(CO)2 radical is slightly bent and has the X2A1 electronic ground state. The present experiment shows that the Co(CO)2 radical is linear in average, and it may probably be a quasi-linear molecule in which the ground state has energy higher than the top of the potential bump.