Pressure broadening coefficients of v(5) fundamental band lines of CH3I at 7 mu m measured by diode laser absorption spectroscopy

摘要

We have measured the room temperature pressure broadening coefficients, gamma, of over 100 lines in five Q-branches of the nu(5) perpendicular band of methyl iodide ((CH3I)-C-12) using tuneable diode laser absorption spectroscopy. The profiles of individual lines in the (P)Q(2), (P)Q(4), (P)Q(5), (P)Q(6) and (R)Q(3) branches were recorded in a 1 m long White cell and at nitrogen or oxygen pressures Lip to 15 Torr. The lines were fitted to the Voigt profile to obtain the collision broadened line widths. Within individual Q-branches the broadening coefficients decreased monotonically with increasing J and for nitrogen broadening varied between 0.19 cm(-1) atm(-1) at low J and 0.12 cm(-1) atm(-1) at high J. The corresponding oxygen broadening coefficients were approximately 20% smaller. Self broadening coefficients were also measured for several of the Q-branches and found to be up to similar to 4 times higher than the corresponding nitrogen broadening values. (C) 2008 Elsevier Inc. All rights reserved.