8- pairs molecules rotated

An important induced dipole component of pairs involving molecules is multipolar induction. Specifically, the lowest-order multipole consistent with the symmetry of H2 is the electric quadrupole. Each H2 molecule may be thought of as being surrounded by an electric field of quadrupolar symmetry that rotates with the molecule.-In that field, a collisional partner X is polarized, thus giving rise to an induced dipole moment which in turn is capable of emitting and absorbing light. For like pairs, molecule 1 will induce a dipole in molecule 2 and 2 will induce one in 1. In... 

Dimers. It is well known that H2 pairs form bound states which are called van der Waals molecules. The discussions above based on the isotropic interaction approximation have shown that for the (H2)2 dimer a single vibrational state, the ground state (n = 0), exists which has two rotational levels f = 0 and 1). If the van der Waals molecule rotates faster ( > 1), centrifugal forces tear the molecule apart so that bound states no longer exist. However, two prominent predissociating states exist which may be considered rotational dimer states in the continuum (/ = 2 and 3). The effect of the anisotropy of the interaction is to split these levels into a number of sublevels. 

Entropy of formation of a pair electrode/molecule Entropy of formation of a molecular pair (rigid rotator)... 

For relaxation in the spin pair IS by the dipolar mechanism in a molecule rotating equally in all directions (isotropically), it can be shown [433,438] that ... 

Debye derived a more general expression from Equation (59) for the interactions between dipolar molecules and induced dipolar molecules (rotating) in 1920. He found that when induction takes place, the pair potential energy between two different dipolar molecules each possessing permanent dipole moments of pi and p2 and polarizabilities a, and ah can be expressed as,... 

This indicates that the molecule rotates, describing a cone the top of which is the sulfur atom. It should seem strange that for dithiols, in which two sulphur atoms are present, the elementary area is smaller, but the reason for it is that the second atom of sulfur plays the part of an anchor and the rotation stops. In this case the molecule is oriented parallel to the surface. Maxted combines structural conceptions with electronic ones, drawing attention to the fact that substances containing atoms with undivided electronic pairs, e.g., a sulfur atom in sulfides, are especially poisonous. 

The high extent of monochromaticity ensures a highly selective action on molecules, for instance, by inducing transitions only between one pair of rotational states. Since the laser line width is often smaller than the isotopic shift of molecular vibration-rotational frequencies, it appears possible to act selectively on iso-topicaUy substituted molecules. This is the basis of laser isotope separation [22, 77, 215, 267]. 

Variational RRKM theory is particularly important for imimolecular dissociation reactions, in which vibrational modes of the reactant molecule become translations and rotations in the products [22]. For CH —> CHg+H dissociation there are tlnee vibrational modes of this type, i.e. the C—H stretch which is the reaction coordinate and the two degenerate H—CH bends, which first transfomi from high-frequency to low-frequency vibrations and then hindered rotors as the H—C bond ruptures. These latter two degrees of freedom are called transitional modes [24,25]. C2Hg 2CH3 dissociation has five transitional modes, i.e. two pairs of degenerate CH rocking/rotational motions and the CH torsion. 

Small molecules in low viscosity solutions have, typically, rotational correlation times of a few tens of picoseconds, which means that the extreme narrowing conditions usually prevail. As a consequence, the interpretation of certain relaxation parameters, such as carbon-13 and NOE for proton-bearing carbons, is very simple. Basically, tlie DCC for a directly bonded CH pair can be assumed to be known and the experiments yield a value of the correlation time, t. One interesting application of the measurement of is to follow its variation with the site in the molecule (motional anisotropy), with temperature (the correlation... 

For vei y small vibronic coupling, the quadratic terms in the power series expansion of the electronic Hamiltonian in normal coordinates (see Appendix E) may be considered to be negligible, and hence the potential energy surface has rotational symmetry but shows no separate minima at the bottom of the moat. In this case, the pair of vibronic levels Aj and A2 in < 3 become degenerate by accident, and the D3/, quantum numbers (vi,V2,/2) may be used to label the vibronic levels of the X3 molecule. When the coupling of the... 

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