LINE MIXING SUM RULES FOR QUASIELASTIC COLLISIONS IN MULTIPLET SPECTRA
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Date
1996
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Ohio State University
Abstract
In the impact approximation, the spectra of transitions overlapped by collisional broadening is given by a sum over Lorentzian absorption and dispersion profiles about each transition. The dispersion components arise from the interference among lines coupled by the collisions, and their magnitude and sign is given by the line mixing coeficient. When the transitions have identical dipole moments and orginate from nearly degenerate energy levels, as often occur in doublet or multiplet spectra, the collisions are quasielastic and the line mixing coefficients sum to zero. Additionally, the sum of the broadening coefficients, the integrated intensities and the shifts are conserved, although these parameters and the line mixing coefficients may be transferred among the multiplet components nonlinearly with pressure. Some illustrative examples of coupled doublets and A, E and F symmetry multiplets in the J manifolds of a spherical top (eg. $CH_{4}$) will be presented along wilh a prescription for incorporating Doppler broadening and Dicke narrowing in experimental spectra.
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Author Institution: Optical Technology Division, National Institute of Standards and Technology