Chapter 5
Interaction-induced Hyperpolarizability
At present, in spite of the well-known fact that the interaction of atoms and
molecules leads to the changing of their multipole moments and (hyper)polarizabilities [1–3], only the simple moments and polarizabilities of interacting molecules such as interaction-induced dipole moments and dipole polarizabilities have
widely studied. Nevertheless, the induced dipole moments and polarizabilities play
the important role in understanding the collision-induced absorption, collisioninduced Rayleigh scattering or collision-induced Raman light scattering [4–9].
Modern calculations of the hyperpolarizabilities of interacting atom-molecular
systems are based on the ab initio methods and analytical models of long-range
multipole-induced multipole interactions. These methods have both advantages and
disadvantages. Analytical models are only effective for interacting systems at large
intermolecular separations, the exchange and other overlap effects can be ignored.
For these separations the hyperpolarizability surfaces can be calculated fully and
correctly if multipole moments, polarizabilities and higher polarizabilities of the
interacting molecules (or atoms) are known. Now, the analytical models are
applied, as a rule, for binary complexes, which are composed of atoms and simple
molecules [10–15].
Ab initio methods, in their turn, allow calculating the hyperpolarizabilities of
interacting systems both for small and large separations. However, when a lot of
points on the (hyper)polarizability surfaces (greed with a small step) are needed the
use of high level ab initio methods becomes often not effective in comparison with
analytical calculations. Such problems can appear, for example, in description of
collision processes. Now, computer methods are widely and effectively used for
calculation of the hyperpolarizabilities both for small atom-molecular systems and
for more complicated atom-molecular systems [16–35] and can be applied to study
nonlinear scattering effects. For instant, there is a lot of publications devoted to the
study of collision-induced hyper-Rayleigh spectra for binary mixtures of noble
gases [36–40], H 2 –Ar and H 2 –He gas mixtures [41, 42], and gaseous SF 6 [43].
© 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_5
83
Interaction-induced Hyperpolarizability
At present, in spite of the well-known fact that the interaction of atoms and
molecules leads to the changing of their multipole moments and (hyper)polarizabilities [1–3], only the simple moments and polarizabilities of interacting molecules such as interaction-induced dipole moments and dipole polarizabilities have
widely studied. Nevertheless, the induced dipole moments and polarizabilities play
the important role in understanding the collision-induced absorption, collisioninduced Rayleigh scattering or collision-induced Raman light scattering [4–9].
Modern calculations of the hyperpolarizabilities of interacting atom-molecular
systems are based on the ab initio methods and analytical models of long-range
multipole-induced multipole interactions. These methods have both advantages and
disadvantages. Analytical models are only effective for interacting systems at large
intermolecular separations, the exchange and other overlap effects can be ignored.
For these separations the hyperpolarizability surfaces can be calculated fully and
correctly if multipole moments, polarizabilities and higher polarizabilities of the
interacting molecules (or atoms) are known. Now, the analytical models are
applied, as a rule, for binary complexes, which are composed of atoms and simple
molecules [10–15].
Ab initio methods, in their turn, allow calculating the hyperpolarizabilities of
interacting systems both for small and large separations. However, when a lot of
points on the (hyper)polarizability surfaces (greed with a small step) are needed the
use of high level ab initio methods becomes often not effective in comparison with
analytical calculations. Such problems can appear, for example, in description of
collision processes. Now, computer methods are widely and effectively used for
calculation of the hyperpolarizabilities both for small atom-molecular systems and
for more complicated atom-molecular systems [16–35] and can be applied to study
nonlinear scattering effects. For instant, there is a lot of publications devoted to the
study of collision-induced hyper-Rayleigh spectra for binary mixtures of noble
gases [36–40], H 2 –Ar and H 2 –He gas mixtures [41, 42], and gaseous SF 6 [43].
© 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_5
83