Chapter 4
Interaction-induced Polarizability
The methods for computation of molecular polarizability are implemented now in
many well-known modern quantum chemical codes. Some of their features will be
discussed in the next Section. And here, we point out the experimental methods
used usually to determine the polarizabilities of atoms, molecules or their complexes. For this purpose, some measured macroscopic properties are used. As a rule,
these properties are some functions of the electromagnetic field which are changing
during the interaction of molecules or atoms with a field. Herewith, the accuracy of
determination of the polarizability depends on the observation methods and the
aggregate state of an environment. The most accurate results are obtained for
incompact gas media.
The most known method to evaluate the polarizability is based on measurements
of the molecular refractivity of any gas. This method allows determining with high
accuracy the average polarizability of molecules [1]. So, for nitrogen and oxygen
molecules the average polarizabilities were measured with the accuracy up to 0.01–
0.03 % [2–6].
Another widespread experimental method uses the changes of parameters for
Rayleigh light scattering. In this way, both invariants of the polarizability tensor
(the average polarizability and the polarizability anisotropy) from the light scattering intensity can be found. However, in practice, the anisotropy polarizability is
preferred for determination by this method. This is because of the fact that for this
case the average polarizability is determined less accurate in comparison with the
refraction method [7, 8]. At the same time, the real accuracy of the polarizability
anisotropy obtained by the use the polarization characteristics of the light scattering
doesn’t exceed of 3–5 %.
The Kerr effect is also often used to determine the polarizabilities of molecules
[1, 9, 10]. In the general case, the Kerr constant has a complicated relation with the
polarizability anisotropy, dipole moment and hyperpolarizability of a molecule. As
a result, the problem of a separation of the contributions to the Kerr constant from
these values is appeared. The separation difficulties lead to the increase of errors of
the method (10–20 %). Only for the gas media composed of non-polar molecules
© The Author(s) 2017
V.N. Cherepanov et al., Interaction-induced Electric Properties of van der Waals Complexes,
SpringerBriefs in Electrical and Magnetic Properties of Atoms, Molecules, and Clusters,
DOI 10.1007/978-3-319-49032-8_4
51
Interaction-induced Polarizability
The methods for computation of molecular polarizability are implemented now in
many well-known modern quantum chemical codes. Some of their features will be
discussed in the next Section. And here, we point out the experimental methods
used usually to determine the polarizabilities of atoms, molecules or their complexes. For this purpose, some measured macroscopic properties are used. As a rule,
these properties are some functions of the electromagnetic field which are changing
during the interaction of molecules or atoms with a field. Herewith, the accuracy of
determination of the polarizability depends on the observation methods and the
aggregate state of an environment. The most accurate results are obtained for
incompact gas media.
The most known method to evaluate the polarizability is based on measurements
of the molecular refractivity of any gas. This method allows determining with high
accuracy the average polarizability of molecules [1]. So, for nitrogen and oxygen
molecules the average polarizabilities were measured with the accuracy up to 0.01–
0.03 % [2–6].
Another widespread experimental method uses the changes of parameters for
Rayleigh light scattering. In this way, both invariants of the polarizability tensor
(the average polarizability and the polarizability anisotropy) from the light scattering intensity can be found. However, in practice, the anisotropy polarizability is
preferred for determination by this method. This is because of the fact that for this
case the average polarizability is determined less accurate in comparison with the
refraction method [7, 8]. At the same time, the real accuracy of the polarizability
anisotropy obtained by the use the polarization characteristics of the light scattering
doesn’t exceed of 3–5 %.
The Kerr effect is also often used to determine the polarizabilities of molecules
[1, 9, 10]. In the general case, the Kerr constant has a complicated relation with the
polarizability anisotropy, dipole moment and hyperpolarizability of a molecule. As
a result, the problem of a separation of the contributions to the Kerr constant from
these values is appeared. The separation difficulties lead to the increase of errors of
the method (10–20 %). Only for the gas media composed of non-polar molecules
© The Author(s) 2017
V.N. Cherepanov et al., Interaction-induced Electric Properties of van der Waals Complexes,
SpringerBriefs in Electrical and Magnetic Properties of Atoms, Molecules, and Clusters,
DOI 10.1007/978-3-319-49032-8_4
51