Self-, nitrogen-, and oxygen-broadening coefficient measurements in the ν1 band of H2O using a difference frequency generation spectrometer at 3 μm

In this paper we investigate the mid-infrared spectrum of the (H2O)-O-16 molecule between 3367 and 3447 cm(-1) to study the gas-collision-broadened linewidths. The coherent radiation used in this experiment is produced through difference frequency generation in a periodically poled lithium niobate crystal. The spectroscopic analysis has concerned nine H2O lines in the v, fundamental vibrational band. For these lines the self-, N-2-, and O-2-broadening coefficients are measured at room temperature. From these data, the widths due to air broadening are also determined. The experimental collisional broadening coefficients are compared with other experimental data and with theoretical calculations based on the Anderson-Tsao-Comutte and Robert-Bonamy theories. Lineshape analysis is performed using both the standard Voigt profile and the Nelkin-Ghatak profile for the hard collision regime. For all the investigated lines the agreement between the Voigt profile and the measured profiles is found to be good. (C) 2002 Elsevier Science (USA).