The vibrational spectrum of α-mercuric sulphide

The Raman spectrum of mercuric sulphide in the α-phase has been studied down to 4 cm−1. The symmetry assignments have been made by examination of the polarization data and by reference to the infrared spectrum. A discussion is given of the observed scattering intensity in a 180° scattering geometry as a near resonance condition is approached. Such a near resonance condition was obtained in mercuric sulphide at room temperature when 6328 Å radiation was used to excite the spectrum. Two phonons at frequencies 96 and 353 cm−1 which have been shown to participate in interband transitions in this crystal have been identified as longitudinal optic phonons of E-symmetry.