Vapour phase Raman spectra of mercury(II) chloride, mercury(II) bromide and mercury(II) iodide. ν 1 (Σ+g) band contours and the mercury—halogen bond polarisability derivatives

The separations of the O and S rotational branches of the ν1(Σ+g) fundamentals of mercury(II) chloride, mercury(II) bromide, and mercury(II) iodide in the vapour phase are found to be in agreement with the predictions of the Placzek–Teller theory. The mercury–halogen bond polarisability derivatives, determined from vapour phase intensity measurements and the appropriate depolarisation ratios, are found to be 2.5 (HgCl), 3.7 (HgBr) and 5.3 (HgI)Å2.