Comment on “Determination of Molecular Quadrupole Moment of Boron Trichloride by Microwave Spectroscopy” [Physica Scripta 67, 525 (2003)]

Abstract

In this Comment, attention is drawn to deficiencies in a recent determination of the magnitude of the molecular quadrupole moment of BCl 3 by the method of foreign-gas microwave pressure broadening, reported by Gierszal, Galica and Mis-Kuzminska [Physica Scripta 67, 525 (2003)].Ã

A computational study of some electric and magnetic properties of gaseous BF3 and BCl3

“…u., respectively, we may comment on previous studies of this property. From our basis-set study, it appears that the split-valence results of Ritchie and co-worker 9,13 are quite far from the MP2 basis-set limit. To illustrate the sensitivity of the quadrupole moment to polarization and diffuse functions in small basis sets, we note that, for the BF 3 molecule, MP2 calculations in the 6-31G, 6-31G * , and 6-31+ G * basis sets give widely different values of 3.83, 2.81, and 3.20 a.u., respectively.…”

“…u. 12 However, questions regarding this work have been raised, 13 highlighting deficiencies in the experimental technique as well as limitations in the approximations made by Gierszal et al The experimentally derived value assumed both a vanishing octupole moment of BCl 3 and a vanishing quadrupole moment of CHF 3 , neither of which are valid assumptions. 23 Clearly, the definitive value of this property has yet to be established.…”

“…9,12,13,24 The calculated and experimental quadrupole moments are listed in Table III, with only the daug-cc -pVXZ results tabulated. Concerning the calculated results, several points are worth making.…”

“…[4][5][6][7][8] The electronic charge structure of these simple molecules has been the subject of recent experimental studies, typically from linear birefringence measurements. [9][10][11][12][13][14] A linear birefringence is the difference in the refractive index along two axes perpendicular to each other and to the direction of propagation of linearly polarized light traversing a sample. It is usually induced by applying static electric and/or magnetic fields with components perpendicular to the direction of propagation.…”

“…Indeed, this was one of the reasons why Ritchie and co-workers chose, among the boron trihalides, to measure the CME of BCl 3 . [9][10][11]13 Still, because of the smallness of the effect in BCl 3 and difficulties in measuring over a broad temperature range, it became necessary to ignore the contribution from temperature-independent terms. In an effort to separate the paramagnetic and diamagnetic contributions to the magnetizability anisotropy of BCl 3 , the lack of an accurate experimental molecular quadrupole moment ⌰ forced Lamb and Ritchie to use a theoretical value, calculated at the second-order Møller-Plesset ͑MP2͒ level of theory in a rather modest Huz-SV basis ͑⌰ = 1.18 a .…”