Multispectrum fits of Ar-broadened HF with a generalized asymmetric lineshape: Effects of correlation, hardness, speed dependence, and collision duration

We analyze the high-resolution asymmetric spectral lines of Ar-broadened HF with a general profile incorporating Dicke narrowing, speed-dependent broadening and shift, and collision-duration effects. Dicke narrowing is characterized by a combination of hard and soft velocity-changing collisions partially correlated with dephasing collisions. The various parameters affect the profiles with a unique pressure dependence and can be determined simultaneously using multispectrum fits. At measurement pressures below an atmosphere, the asymmetries are dominated by the Dicke correlations, with the speed-dependent shifts playing a secondary role. Here, the dispersive effects of collision duration are barely determinable and somewhat uncertain due to their sensitivity to the model. (C) 2001 Academic Press.