Computer controlled diode laser spectrometer with a helium evaporation cryostat and spectroscopy of thev3 vibration of NCO

A computer-controlled diode laser spectrometer for the 1200 to 2500 cm−1 spectral region is described. The spectrometer has been applied to high resolution spectroscopy of the NCO radical at 5.2 μm. The lead-salt diode lasers are cooled to their operating temperature with a temperature adjustable helium evaporation cryostat. Computer-controlled tuning procedures for the frequency tuning of the diode lasers have been developed; they are independent of tables describing the tuning characteristics of the diode lasers. 41 lines of the antisymmetric stretching-vibrationv3 of the linear NCO radical have been observed. We were able to detect vibration-rotation transitions in both2π1/2 and2π3/2 fine structure sublevels. These measurements led to the precise determination of additional molecular constants.