Quadrupoles, electronic, electrostatic interactions

In addition, the electron cloud in an atom may have an electrostatic interaction with the electric quadrupole moment of the nucleus, if one exists. This effect is very small (of the order of 10 cm. ). Finally there is the energy of the direct interaction of the nuclear moment with the external magnetic field ( 10 cm. ) as in NMR. 

The nuclear spins give rise to additional terms in the Breit-Pauli Hamiltonian due to the interaction of the electrons with the magnetic moment of the nuclei and the electrostatic interaction with the electric quadrupole interaction of the nuclei. The magnetic interaction term of the spins with the nuclei is of the same type as the spin-spin interaction and following Abragam and Pryce (61) can be written as... 

The intermolecular forces of adhesion and cohesion can be loosely classified into three categories quantum mechanical forces, pure electrostatic forces, and polarization forces. Quantum mechanical forces give rise both to covalent bonding and to the exchange interactions that balance tile attractive forces when matter is compressed to the point where outer electron orbits interpenetrate. Pure electrostatic interactions include Coulomb forces between charged ions, permanent dipoles, and quadrupoles. Polarization forces arise from the dipole moments induced in atoms and molecules by the electric fields of nearby charges and other permanent and induced dipoles. 

The distinguishing feature of dehydrated zeolites as microporous aluminosilicate adsorbents lies in the presence in their voids—i.e., micropores—of cations. These cations compensate excess negative charges of their aluminosilicate skeletons. The cations form, in the zeolite micropores, centers for the adsorption of molecules with a nonuniform distribution of the electron density (dipole, quadrupole, or multiple-bond molecules) or of polarizable molecules. These interactions, which will be called, somewhat conventionally, electrostatic interactions, combine with dispersion interactions and cause a considerable increase in the adsorption energy. As a result, the adsorption isotherms of vapors on zeolites, as a rule, become much steeper in the initial regions of equilibrium pressures as compared with isotherms for active carbons. 

In nonspherical nuclei (/ > i) there exists a nonzero quadrupole moment for the nuclear charge density that contributes to the quadrupolar term (fourth term) in Eq. (1). In the expression for the electrostatic interaction energy for the nucleus in the potential produced by the electrons, the electric quadrupole moment of the nucleus is coupled to the gradient of the electric field at the nuclear site. This field gradient is, of course, due to the electrons. In diagonalized form one may write... 

In addition to the diffusive forces and effects of an external electric field mentioned, ion motion in an IMS drift tube is affected by the electrostatic interactions between the ion and the gas molecules of the supporting atmosphere. The electron cloud surrounding the neutral gas molecule is polarized by the ion, thus inducing a dipole moment in the neutral molecule. This results in an electrostatic interaction between the ion and the neutral molecule the ion-induced dipole effect. Furthermore, molecules that have permanent dipole or quadrupole moments will be attracted to the ion through ion-dipole or ion-quadrupole interactions. 

It is usual in magnetic solids for the main influence on the Mdssbauer spectrum to be felt through the interactions [1] and [2]. That is, the nucleus senses its own atom and the state of the solid via the effect of the solid on that atom. The interactions of class [1] are (i) the magnetic hypeifine interaction between the atomic spin S and the nuclear spin /, (ii) the interaction between the nuclear quadrupole moment Q (which is proportional to the deviation from a spherical distribution of nuclear charge) and the electric field gradient (EFG) produced by the electronic charge distribution of the atom, and (iii) the electrostatic interaction of the... 

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