Single-crystal infrared study and assignment for mercury(II) chloride and bromide

Abstract

A study of HgCl₂ and HgBr₂ has been made using single-crystal i.r. reflectance (115 and 295 K) and absorption (295 K) methods. All the fundamentals predicted by factor-group analysis have been observed and assigned to their symmetry species for both materials. Existing single-crystal Raman data have been accounted for in detail in the case of HgCl₂. Infrared bands at 32 and 40 cm^–1 in HgCl₂ are attributed to translatory modes, and it is probable that the ν₂ components are at higher frequencies than the libratory lattice modes. The lack of single-crystal Raman data for HgBr₂ requires the deferment of the assignment of all the details of the Raman spectra from polycrystalline samples, and is desirable for confirmation of weaker features in the i.r. spectra.