15min:

YUTAKA MIYAMOTO, ZDENEK ZELINGER, YOSHIHIRO NAKASHIMA AND KEIICHI TANAKA, Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, 812-8581 JAPAN.

The visible and near infrared emission spectrum in the 480 - 900 nm region of ICN⁺ was measured by Fourier transform spectrometer (Bruker IFS 120HR). The ICN⁺ was produced by Penning ionization of ICN with metastable He*. The ICN⁺ ion has much larger spin-orbit interaction constant (A=-4343 cm^-1) than those of the ClCN⁺(-276 cm^-1) and the BrCN⁺(-1477 cm^-1)\footnoteJ. Fulara et al. , J. Phys. Chem. , 89, 4213-4219, (1985). The Renner-Teller effect appears in the ₂ excited state of X² . It is interesting to study the Renner-Teller effect of ICN⁺. Eight vibronic bands of the A^{2 +}-X² transition (both for the =1/2 and 3/2 spin components) of ICN⁺ were observed. So far, the rotational analysis was performed for two vibronic bands, A^{2 +}(000) -X² _3/2(000) and A^{2 +}(000) - µ² (010). Molecular constants, including the band origin, the effective rotational constant, centrifugal distortion constant and spin-rotation interaction constant, were determined for the A^{2 +} and X² _3/2 states.

Due to the Renner-Teller effect, the X² (010) state was split into four vibronic components, µ² , ² , and ² _P(P=3/2 and P=5/2). For the A^{2 +} - µ² band, P₁, P₂, R₁ and R₂-branch were observed. For the µ² vibronic state, -type doubling constant was determined as well as the rotational constant and centrifugal distortion constant. Renner parameter for the X² state was determined to be -0.197 from the -type doubling constant. The determined Renner parameter ( =-0.197) was close to that of BrCN⁺(-0.185). We are now analyzing the spectrum for the =1/2 spin component, A^{2 +}(000) -X² _1/2(000) and A^{2 +}(000) - ² (010), to study the Renner-Teller effect in more detail.