“…In addition, under conditions of low and intermediate ratios of the collisional width, Γ , to the Doppler width, Γ D , the lineshape affected by the speed dependence of collisional broadening can often be well modeled by the Dicke narrowed profile. 41,55 Unfortunately, this treatment leads to a nonlinear pressure dependence of the narrowing parameter Re(ν opt ) 14,56,57 in this intermediate case (i.e., 1 < Γ /Γ D < 5). This nonphysical result can be seen in the R(24) NGP fit shown in Fig.…”