15min:

YOSHIHIRO NAKASHIMA, KEIICHI TANAKA AND TAKEHIKO TANAKA, Department of Chemistry, Faculty of Science, Kyushu University 33, Hakozaki, Higashiku, Fukuoka 812-8581, Japan..

The OCS⁺ ion was produced by Penning ionization of OCS with metastable He^*, and UV emission in the 370~-~500~nm region was measured by Fourier transform spectrometer. The A² - X² electronic transition has been reported in the 300~-~500~nm region, but only the emission bands from the vibrational ground state of the A² state were observed because of the predissociation in the ² state \hspace*0mm . High resolution study of the 0-0 band has been reported for both the =3/2 and =1/2 spin states \hspace*0mm ^, \hspace*-1mm .

In the present study, seven rotationally resolved bands were observed in the 370~-~500~nm region and assigned to the CO stretch ( ₃'') progression : A² _3/2(000) - X² _3/2(00v)~(v=2-5) and A² _1/2(000) - X² _1/2(00v)~(v=3-4). The observed lines of the =1/2 substate were split into the two components due to the -type doubling. The spectra for =3/2 and =1/2 were analysed separately to obtain molecular constants for each spin state.

Band origins, vibrational frequencies, rotational constants, vibrational-rotational constants for both spin substates and -type doubling constant for the =1/2 substate were determined by a least squares fitting. Rotational constants in the vibrational ground state were determined for both spin states. The spin-orbit interaction constants derived from these rotational constants, A'=-125.0~cm^-1 and A''=-383.8~cm^-1, are consistent with those derived from the photodissociation study \hspace*0mm .