BROADENING AND SHIFTING OF THE RAMAN Q-BRANCH IN D-2 AND D-2-HE MIXTURES .2. LINE-SHAPES, FITTING ROUTINES, AND EFFECTS NONLINEAR IN DENSITY

In the preceding paper we fitted the experimental profiles using a sin gle Lorentzian line shape and assumed that the width and shift were pr oportional to the density. Here we discuss nonlinear contributions to widths and shifts and present a different spectral profile and analysi s that allows us (i) to determine unbiased, binary collision, impact L imit, broadening and shifting coefficients; (ii) to disentangle severa l effects nonlinear in the density; and, subsequently, (iii) to observ e broadening and shifting arising purely from the correlation between perturbers and three-body interactions. This is a new avenue of resear ch in molecular dynamics. In addition, measurements of the broadening of the depolarized part of the Q branch in D-2 are reported for the fi rst time.