Microwave spectroscopy of the NCO radical in thev2= 12Σ state

Abstract

The microwave spectra of the NCO radical in the (0, 1, 0) μ 2Σ and (0, 1, 0) κ2Σ states have been observed by using a source-frequency modulation spectrometer. The radical was generated by the reaction of HNCO with microwave discharge products of CF4. The observed spectra were analysed using a hamiltonian that included the interactions of the (0, 1, 0) state with (1, 1, 0), (0, 1, 1) and (0, 3, 0), and the rotational, spin-rotation, centrifugal distortion, rovibronic interaction and hyperfine coupling constants were determined precisely for the (0, 1, 0) μ 2Σ and (0, 1, 0) κ2Σ states. From the rovibronic interaction constants two anharmonic potential constants W 1 and W 2 were calculated to be 29·5 (1) and 3·3 (1) cm-1, respectively, with three standard errors in parentheses. The effective B rotational constant in the (0, 1, 0) 2Σ state was found to differ by 1·99 (12) MHz from that in the (0, 1, 0) 2Δ state previously reported. This difference was accounted for by higher order rovibronic interactions; an algebraic expression was derived for the difference. This formula was applied also to BO2, CNC, CCC and CO2 +. For BO2 and CNC the calculated values agreed well with the observed values, whereas discrepancies remained for CCC and CO2 +.