Diatom complexes

The dipole-inducing mechanims of simple binary systems, such as atom-atom, atom-diatom, and diatom-diatom complexes with limited numbers of electrons, are well understood. For example, the exchange force-induced and dispersion-force-induced dipole components have been accurately computed for several simple systems, using quantum chemical methods (Chapter 4). The classical multipolar induction scheme is well known since the discovery of interaction-... 

In this section we will explain the essential mechanism of vibrational predissociation by virtue of a linear atom-diatom complex such as Ar H2. Figure 12.1 illustrates the corresponding Jacobi coordinates, t In particular, we consider the excitation from the vibrational ground state of H2 to the first excited state as illustrated in Figure 12.2. The close-coupling approach in the diabatic representation, summarized in Section 3.1, provides a convenient basis for the description of this elementary process. For simplicity of presentation we assume that the coupling between the van der Waals coordinate R and the vibrational coordinate r is so weak that it suffices to include only the two lowest vibrational states, n = 0 and n = 1, in expansion (3.4) for the total wavefunction,... 

Here, an and a are the polarizabilities of the diatomic complex parallel and perpendicular to the internuclear separation, R12. A purely classical theory, which accounts for the electrostatic distortion of the local field by the proximity of a point dipole (the polarized collisional partner), suggests that )S(Ri2) 6ao/Ri2 with (Xq designating the permanent polarizability of an unperturbed atom. This expression is known to approximate the induced anisotropy of such diatoms fairly well. This anisotropy gives rise to the much studied pressure-induced depolarization of scattered light and to depolarized CILS spectra in general. The depolarization of light by dense systems of spherical atoms or molecules has been known as an experimental fact for a long time. It is, however, discordant with Smoluchowski s and Einstein s... 

The extended geminal models have been used to calculate the interatomic potential for the ground state of diatomic complexes comprising an alkali ion and a noble gas atom NeLi+ [33] ArLi+ [34] ArNa+, NeNa+, HeNa+ [35] HeKa+ [36]. On the basis of the potentials for NeLi+ and HeKa+, mobility coefficients were calculated [37,38]. There was a very good agreement between the calculated and measured mobility coefficients. The deviation being of the order of 1% or lower. 

The infrared transitions in the atom-diatom complexes will obey the following selection rules Ap = 1, and AJ = 1 or 0. Additionally, if the energy levels can be labeled with the quantum numbers j and 1, the selection rules A/ = 0 and Aj = 1 should hold approximately. 

It is known that the solution molecule interacts with the solute molecules via so called polarization or van der Waals forces. These forces are also active in the formation and binding of nobel-gas-diatom complexes. This kind of interaction is so weak that the vibrational and rotational motion of the diatomic in the van der Waals complex is similar to that of the free diatomic. A van der Waals system of the kind AB — X is thus considered to be a good candidate as model system for these studies of solute - solvent interaction. 

Consider the reaction of two atoms to form an activated complex A + B (AB). Write the partition functions for the atoms and the diatomic complex and show that the frequency factor predicted by the Eyring equation is identical to that predicted by the collision theory if j- b, the interatomic distance in the complex, is identified with [Pg.866]

Modified method of the diatomic complexes in molecules , which provides a satisfactory prediction of the valent-bound atoms interaction at the stages of chemical adsorption of catalytic system components and monomer molecules, reactions of initiation and chain growth in a-olefins, and 1,3-dienes stereospecific polymerisation reactions. 

The coordinate system needed for an atom-nonlinear molecule complex is a straightforward generalisation of that for an atom-diatom complex. The body-fixed axis system is defined as before, with Euler angles (a,, 0) specifying the orientation of R. However, it is now necessary to define an axis system (x y z) fixed in the monomer the relationship of these axes to the body-fixed axes is specified by Euler angles (0,, x)- md 0 describe the orientation of the z axis, and x describes rotations about the 2 axis. 

For a diatom-diatom complex, there are three sources of angular momentum the rotation of each of the monomers, characterised by quantum numbers ji and j2, and the end-over-end rotation of the complex as a whole. There are at least two ways of formulating the diatom-diatom problem in body-fixed coordinates. In the one which displays most clearly the similarity to atom-diatom systems, ji and j 2 are first coupled together to form a resultant h... 

In this chapter we present an account of our recent work on unimolecular ET of a model diatomic complex and SnI ionization of t-BuCl in RTILs. Despite their relatively low dielectric constant, RTILs have a pronounced effect on reaction free energetics and thermodynamics of these processes because of strong electrostatic coupling of their ions with the solute charge transfer and shift. This finding is in concert with large solvatochromic shifts and thus high empirical solvent polarity of RTILs observed in many experimental and simulation studies. 

Here a is defined by the effective mass of the three-atom system g and the reduced mass ggQ of the diatomic complex BC ... 

The dipole moments of the atom-diatomic complexes X2-Y, in contrast to the atom-atomic ones, depend also on the angle 0 between the axis of diatomic molecule and the axis passing through the atom Y and the molecule X2 (Fig. 3.2a). Note that if the nonrigidity of the diatomic molecule X2 is taken into account, then the additional dependence of dipole moment of the complex on r appears. So, in general we have a surface of the dipole moment for such complex. Nevertheless, these van der Waals complexes are relatively simple yet and they are studied intensively up to now because of their importance (see, for instance, [24—30]). 

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