Interaction electronic-vibrational

Electronic structure theory describes the motions of the electrons and produces energy surfaces and wavefiinctions. The shapes and geometries of molecules, their electronic, vibrational and rotational energy levels, as well as the interactions of these states with electromagnetic fields lie within the realm of quantum stnicture theory. 

The interaction of a molecular species with electromagnetic fields can cause transitions to occur among the available molecular energy levels (electronic, vibrational, rotational, and nuclear spin). Collisions among molecular species likewise can cause transitions to occur. Time-dependent perturbation theory and the methods of molecular dynamics can be employed to treat such transitions. 

These so-called interaction perturbations Hint are what induces transitions among the various electronic/vibrational/rotational states of a molecule. The one-electron additive nature of Hint plays an important role in determining the kind of transitions that Hint can induce. For example, it causes the most intense electronic transitions to involve excitation of a single electron from one orbital to another (recall the Slater-Condon rules). 

The use of molecular and atomic beams is especially useful in studying chemiluminescence because the results of single molecular interactions can be observed without the complications that arise from preceding or subsequent energy-transfer coUisions. Such techniques permit determination of active vibrational states in reactants, the population distributions of electronic, vibrational, and rotational excited products, energy thresholds, reaction probabihties, and scattering angles of the products (181). 

If we deal with N isolated non-interacting entities such as the molecules in a gas at low density, we can further divide up molecular energies with reasonable accuracy into their electronic, vibrational and rotational contributions... 

INTERACTIONS OF VIBRATION ALLY-EXCITED MOLECULES AT SURFACES A PROBE FOR ELECTRONICALLY NONADIABATIC EFFECTS IN HETEROGENEOUS CHEMISTRY... 

The proviso T = 0 signifies that AB is in its electronic, vibrational, and rotational ground states and has no translational energy. The word isolated indicates the perfect gas model. The minimum energy condition ensures that AB+ is also in its electronic, vibrational, and rotational ground states and the translational energies of AB+ and e are both zero it also indicates that the products in reaction 4.1 do not interact, that is, they also conform with the perfect gas model. 

I have predicted that the very unusual low-frequency IR behavior for the Creutz-Taube ion calculated by Piepho, Schatz and Krausz [Piepho, S. B. Krausz, E. R. Schatz, P. N. J. Am. Chem. Soc. 1978, 100, 2996] on the assumption of only antisymmetric mode involvement in electron-vibrational interaction would not be found, and that it was an artifact of the method. The failure of experiments designed to locate such IR bands has subsequently been reported by Krausz, et al. 

Spectroscopy produces spectra which arise as a result of interaction of electromagnetic radiation with matter. The type of interaction (electronic or nuclear transition, molecular vibration or electron loss) depends upon the wavelength of the radiation (Tab. 7.1). The most widely applied techniques are infrared (IR), Mossbauer, ultraviolet-visible (UV-Vis), and in recent years, various forms ofX-ray absorption fine structure (XAFS) spectroscopy which probe the local structure of the elements. Less widely used techniques are Raman spectroscopy. X-ray photoelectron spectroscopy (XPS), secondary ion imaging mass spectroscopy (SIMS), Auger electron spectroscopy (AES), electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spectroscopy. 

The Time Dependent Processes Section uses time-dependent perturbation theory, combined with the classical electric and magnetic fields that arise due to the interaction of photons with the nuclei and electrons of a molecule, to derive expressions for the rates of transitions among atomic or molecular electronic, vibrational, and rotational states induced by photon absorption or emission. Sources of line broadening and time correlation function treatments of absorption lineshapes are briefly introduced. Finally, transitions induced by collisions rather than by electromagnetic fields are briefly treated to provide an introduction to the subject of theoretical chemical dynamics. 

Fig. 7 Reorganization of tunneling barrier for the transfer of electrons, interacting with vibrations in different regimes of slow, intermediate, and fast tunneling [90]. The dot-dash, dash, and solid lines refer (respectively) to COytt=0A, 1.0, and 10.0, see text in Sect. 7...

H — H°. The perturbation H contains interaction terms between the electronic, vibrational, and rotational motions, and adds a correction term to the simple product wave function ... 

In linear molecules, the electronic-rotation interaction terms in H cause the A-type doubling of electronic states, whereas the vibration-rotation interaction terms in H cause the /-type doubling of vibrational states. In addition, the perturbation H can cause interactions between vibration-rotation levels of different electronic states. If it happens that two vibration rotation levels of different electronic states of a molecule have... 

Recent advances in experimental techniques, particularly photoionization methods, have made it relatively easy to prepare reactant ions in well-defined states of internal excitation (electronic, vibrational, and even rotational). This has made possible extensive studies of the effects of internal energy on the cross sections of ion-neutral interactions, which have contributed significantly to our understanding of the general areas of reaction kinetics and dynamics. Other important theoretical implications derive from investigations of the role of internally excited states in ion-neutral processes, such as the effect of electronically excited states in nonadiabatic transitions between two potential-energy surfaces for the simplest ion-molecule interaction, H+(H2,H)H2+, which has been discussed by Preston and Tully.2 This role has no counterpart in analogous neutral-neutral interactions. 

Energy transfer occurring in nonreactive neutral-neutral collisions is a very active field of investigation.230 Important contributions to the understanding of collisional energy-transfer processes have also resulted from various studies of nonreactive ion-neutral collisions. The modes of energy transfer that have been investigated for the latter interactions include vibrational to relative translational (V-T), vibrational to vibrational (V-V), translational to vibrational (T-V), translational to rotational (T-R), vibrational to rotational (V-R), translational to electronic (T-E), and electronic to translational (E-T). 

There are several nonadiabatic interactions (see the appendix), for example, electron-vibration coupling and spin-orbit interaction. The electron-vibration interaction is described by the operator ... 

Owing to the electron-vibrational interaction in molecules, there is one more possible decay channel for SES. This is the nonradiative relaxation (internal conversion), in which the electron energy is transferred into vibrational energy of molecules (in the condensed phase, into thermal energy of the medium). If the molecule fluoresces, there may also occur fluorescence from the lowest excited state. (According to the empirical rule of Kasha,64 the molecular fluorescence occurs from the lowest excitation level irrespective of the wavelength of the exciting radiation.)... 

Abstract Theory of non-adiabatic electron-vibration interactions has been applied to the... 

The non-adiabatic theory indicates that electron - vibration (phonon) interaction, at stabilization (minimization) of the fermionic ground state... 

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