Rayleigh depolarization ratios and molecular polarizability anisotropies of BX3 (X=F, Cl, Br, I). Comparison of experimental results and ab initio calculations

Improved equipment for measurements, at elevated temperatures, of the vapour-phase Rayleigh depolarization ratios of relatively involatile and weakly anisotropic species is described. Analysis of the depolarization ratios in conjunction with the known mean polarizabilities gives values (in 10−40 C m2 V−1) of the polarizability anisotropies, Δα(=αzz−αxx), of BF3 (−0.63±0.03), BCl3 (−3.55±0.11) and BBr3 (−5.65±0.18); the correlation between the longitudinal polarizability and the cube of the bond length then yields Δα for BI3 (−9.0). As well, ab initio calculations of the polarizabilities, and also the quadrupole moments, of BF3, BCl3, BBr3 and BI3 at the SCF and MP2 levels of theory with the HUZ-SV (+sd) basis set are reported.