Infrared laser magnetic resonance spectroscopy of free radicals in the gas phase

Infrared transitions of free radicals have been studied in the 5 - 7 micron region using a carbon monoxide laser magnetic resonance spectrometer. Some details of the spectrometer and problems involving the laser source are discussed and spectra are reported due to the SeD and NCO free radicals. Two very different infrared transitions in SeD are reported and analysed. These are direct transitions between the two fine structure states of the 21[ ground electronic state and fundamental vibration rotation transitions between the 2113/2 substates. The spectra are analysed in terms of the effective Hamiltonian for a 211 electronic state and the effect of the interaction between the nearby 21[3/2 (v n 1) and2111/2 (v - 0) levels is taken into account to determine some of thesmaller molecular parameters. For the vibration rotation spectra absorptions due to species containing different naturally occurring selenium isotopes were analysed simultaneously to allow the determination of the vibrational band origin (vo . 1677.05090 (16) cm-1 ) and the anharmonicityWexe. Vibration rotation transitions in the v3 fundamental of the NCO radical are also reported and analysed to give a value of 1920.60645 (19) cm 1 for the band origin. A single transition in the (0,1,1) w (0,1,0) hot band which was recorded subsequently is also analysed to give the hotband origin as 1907.11892 (20) cm 1.