Molecular quadrupole moment

Figure 4.18 from Buckingham A D 1959. Molecular Quadrupole Moments. Quarterly/ Reviews of the Chemical Society 13 183-214. Reproduced by permission of The Royal Society of Chemistry. 

Microwave spectra obtained from PHgD and PHDa in a magnetic field of about 25 kG showed Zeeman effects, from which molecular g values were calculated. They were 20 times smaller than those for ammonia. The molecular quadrupole moments of phosphine and ammonia were approximately the same. Magnetic susceptibilities and molecular quadrupole moments were also compared. 

Flygare, W.H. and Benson, R.C. (1971). The molecular Zeeman effect in diamagnetic molecules and the determination of molecular magnetic moments (g values), magnetic susceptabilities, and molecular quadrupole moments, Mol. Phys., 20, 225-250. 

Buckingham AD (1959) Molecular quadrupole moments. Quart Rev Chem Soc (London) 13 183-214... 

Nuclear quadrupole moments are conventionally defined in a different way from molecular quadrupole moments. Q is an area and e is the elementary charge. eQ is taken to be the maximum expectation value of the zz tensor element. The values of Q for some nuclei are listed in table 6.3. 

Differences in CC bond lengths of the aromatic moiety, which are less than 0.025 A are indeed small if compared to distances of 1.48 A and 1.33 A characterising C(sp2)-C(sp2) single and C(sp2)=C(sp2) double bonds, respectively, as usually pointed out by X-ray researchers. However, they are quite significant for many properties which critically depend on interatomic distances like e.g. molecular quadrupole moments, electric field gradients, spin-spin coupling constants of directly bonded atoms etc. A... 

For example, Bosomworth and Gush have measured induced absorption in Hs, Ns, and Oj, confirming with improved precision measurements on Na made by Gebbie and his co-workers. Poll had used these to find a quadrupole moment for Na in good agreement with a wave-mechanical estimate, suggesting that quadrupole induction in fact predominates for Na. The measurements on Oa, on the other hand, show a very broad absorption in spite of a low molecular quadrupole moment, implying dominance of overlap effects in this case. For both Na and Oa, rotation and translation absorptions overlap entirely, but in Ha at 77 K rotation is well separated from the weak, low-frequency translation-absoj ition band. 

Dielectric and pressure virial coefficients of NzO have been measured at 6.5, 30.1, and 75.1 °C. The dipole moment, polarizability, and molecular quadrupole moment were determined to be 0.18 D, 3.03 x 1CT24 cm3, and 3.4 xlO 26 e.s.u. cm2, respectively.91 A lower limit of —0.15 0.1 eV has been calculated for the molecular electron affinity of N20, using molecular beam studies.92 The enthalpy-pressure behaviour for N20 along eleven isotherms in the vapour phase has been determined from measurements of the Joule-Thomson effect.91... 

Mhin et al. [148] used a molecular quadrupole-moment parameter to describe the electrostatic interaction of polychlorinated dibenzo-p-dioxins at the Ah receptor active site. Their analysis suggests that the most potent molecules have a high polarizability across the lateral direction. 

Mhin BJ, Lee JE, Choi W. Understanding the congener-specific toxicity in polychlorinated dibenzo-p-dioxins Chlorination pattern and molecular quadrupole moment. J Am Chem Soc 2002 124 144-8. 

Coriani, S., Halkier, A., Rizzo, A. The electric-field-gradient-induced birefringence and the determination of molecular quadrupole moments. In Pandalai, G. (ed.) Recent Research Developments in Chemical Physics, Vol. 2, pg. 1, Transworld Scientific, Kerala, India (2001)... 

Ritchie, G.L.D. Field-gradient induced birefringence a direct route to molecular quadrupole moments. In Clary, D.C., Orr, B., (eds) Optical, Electric and Magnetic Properties of Molecules, pg. 67, Elsevier, Amsterdam, The Netherlands (1997)... 

The diagonal elements of the molecular quadrupole moment tensor Q are related to the diagonal elements of the magnetic susceptibility tensor in Eq. (10) by3... 

We now recall that only the value of the first non-zero electric multipole moment is independent of the origin. Consider a molecular quadrupole moment along the internuclear z axis in a linear molecule at two different origins along the z axis separated by Z. According to Eq. (12)... 

The uncertainties in the molecular quadrupole moments in Tables 1 and 2 calculated with Eq. (11), (12), or (13) depend in most cases on the uncertainties in the magnetic susceptibility anisotropies as the g values are normally the more accurate Zeeman parameter. It is evident from Table 1 that the determination of the sign of the electric dipole moment is a marginal experiment as the standard deviations are normally as large as the measured moments. Nevertheless, most of the di-... 

TABLE 1 Molecular g Values, Electric Dipole Moments (and Signs), Magnetic Susceptibility Anisotropies, and Molecular Quadrupole Moments of a Number of Linear and Symmetric Top Molecules as Measured by Microwave Spectroscopy... 

TABLE 5 Calculated Molecular Dipole Moments, Molecular Quadrupole Moments, Second Moments of the Electronic Charge Distribution, and Diamagnetic Susceptibilities ... 

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