Figure 3. A plot of A(v)/ρ2 versus the frequency (cm-1) measured using an FIR interferometer and indicated by the solid curve. The results are displayed for the four different temperatures used: (a) 212 K, (b) 179 K, (c) 149 K, (d) 126 K. In each case the laser measurements at 84.2 and 15.1 cm-1 are shown. Also shown are the theoretical line shapes generated using Mori theory (dashed line) as discussed in the text. In (d) the results of Buontempo et al. (10) are given for comparison.