H.-D. Kronfeldt

Three channel diode laser spectrometer for the determination of line-shift coefficients in the ν3 band of NO2

The implementation of a three channel lead salt diode laser spectrometer and its application for the measurement of line-shift coefficients in the ν3 band of NO2 are presented. The spectrometer allows the determination of line shifts larger than 5.10−4 cm−1 and is suitable also for the investigation of relatively crowded spectra of molecules like NO2 or SO2. For the first time it was possible to determine shift coefficients for seven lines of the ν3 band of NO2 in the case of collisions with He, Ne, Ar, Kr, and Xe. Moreover, the spin splitting and the relative intensity of the doublet components were measured for eight unresolved doublets. The shift and broadening coefficients were determined for lines covering the quantum number ranges 24 ⩽ N″ ⩽ 38, 1⩽ Ka″ ⩽ 5, the spin splittings and the intensity ratios for lines within the intervals 20 ⩽ N″ ⩽ 38, 1 ⩽ Ka″ ⩽ 5. The broadening data show an excellent agreement with experimental data recently published. The results for the spin splitting correspond to the theoretical expectation, the intensity ratios are in good agreement with experimental and theoretical data. These coincidences are prerequisite for the validation of the line-shift data. All shift coefficients measured are negative; in the best cases the uncertainties were less than 2%. The absolute values of the line-shift coefficients for the different noble gases follow the trend ¦δNO2He¦<¦δNO2¦<¦δNO2Ar¦ <¦δNO2Kr¦<¦δNO2Xe¦. Within the studied quantum number range an increase of the absolute size ¦δNO2noble gas¦ with increasing N″ is observed.