Second-Order Raman Spectrum of Germanium

The second-order Raman spectrum of crystalline germanium has been observed. Measurements were performed for several incident- and scattered-light polarizations so as to separate the three independent components of the Raman tensor. Interpreted in the light of recent neutron-scattering work by Nelin and Nilsson, the ${\Gamma }_1$ spectrum corresponds to overtone two-phonon processes. Overtone and combination processes are seen for the ${\Gamma }_{25}$, and ${\Gamma }_{12}$ components.