Two-phonon difference scattering in solid xenon

We have measured the complete second-order Raman spectrum of solid xenon at two temperatures: 125 and 156 K. In addition to the familiar two-phonon sum processes, we have carefully measured the spectrum of two-phonon difference processes, which produce a central peak, whose linewidth is temperature dependent. At 156 K the width is 6.8 ${\mathrm{cm}}^{-1\mathrm{}}$, while at 125 K it is 4.3 ${\mathrm{cm}}^{-1\mathrm{}}$, half-width at half maximum (HWHM). Comparison with recent calculations suggests that the observed anharmonic effects are significantly larger than expected and that such experimental results may provide a sensitive test for the interatomic potential of solid rare gases.