Resonant Raman scattering of red-HgI2inB-exciton and band-to-band transition regions

Our previous analysis of resonant Raman spectra in the $A$-exciton region of red-Hg${\mathrm{I}}_2$ at 4.2 K is extended to the wavelength range of the $B$-exciton and of the band-to-band transition. According to the grouptheoretical analysis and energy-momentum conservation laws, the present experimental results can give assignments of phonon modes in the second-order Raman processes. In the band-to-band transition region, we find multiple scattering of hot carriers by the $E$-mode phonons. One may give these new assignments of higher-order scattering processes for the first time in this layer-type semiconductor, thanks to improved spectral resolution.