SPECTRAL LINE-BROADENING

Burshtein A. I., Naberukhin Yu. I. Phase-memory effects in the theory of spectral line broadening in gases. Sov. Phys. JETP. 25, 799-805 (1967) [ZhETF, 52, 1202-11 (1967)]. 

Griem H. Spectral Line Broadening by Plasma. (Academic Press, New York) (1974) [Russian translation (Mir, Moscow) p. 186 (1978)]. 

Smith E. W., Giraud M., Cooper J. A semiclassical theory for spectral line broadening in molecules, J. Chem. Phys. 65, 1256-67 (1976). 

Perhaps the first evidence for the breakdown of the Born-Oppenheimer approximation for adsorbates at metal surfaces arose from the study of infrared reflection-absorption line-widths of adsorbates on metals, a topic that has been reviewed by Hoffmann.17 In the simplest case, one considers the mechanism of vibrational relaxation operative for a diatomic molecule that has absorbed an infrared photon exciting it to its first vibrationally-excited state. Although the interpretation of spectral line-broadening experiments is always fraught with problems associated with distinguishing... 

Table 4.1. Various processes contributing to the spectral line broadening for local vibrations. Frequencies of collectivized local vibrations QK (solid arrows) are supposed to exceed phonon frequencies oiRq (dashed arrows) Ok > max oncq. For an extremely narrow band of local vibrations, diagrams A and B respectively refer to relaxation and dephasing processes, whereas diagrams C account for the case realizable only at the nonzero band width for local vibrations.

A rigorous treatment of the IR-absorption spectral line broadening for valence vibrations of a reorienting group should include, in addition to reorientational... 

Yeh and Keeler 244) extended the method of laser-scattering spectroscopy to probe systems undergoing rapid chemical reactions. They observed the spectral line broadening in light from a singlemode He-Ne laser scattered from multicomponent solutions, as a function of time. The experiment employed a pressure-scanned Fabry-Perrot interferometer and photon counting techniques. 

As indicated previously, NMR may be used simply as an analytical technique for monitoring the decomposition of a reactant or formation of a product. In addition, NMR and ESR merit a special mention due to their importance in studying the dynamics of systems at equilibrium these so-called equilibrium methods do not alter the dynamic equilibrium of the chemical process under study. They have been used to study, for example, -transfer reactions, valence isomerisations, conformational interconversions, heteronuclear isotopic exchange processes (NMR) and electron-transfer reactions (ESR). These techniques can be applied to the study of fast or very fast reactions by analysis of spectral line broadening [16,39],... 

H.R. Griem, Spectral Line Broadening by Plasmas, Academic Press, New York, 1974. 

The relationship between spectroscopic and statistical functions has been exploited for a variety of phenomena related in different ways to the dynamical response of the medium. We cite as examples spectral line broadening, photon echo spectroscopy and phenomena related to TDFSS we are examining here. A variety of methods are used for these studies and we add here methods based on ab initio CS. The basic model is actually the same for all the methods in use ab initio CS has the feature, not yet implemented in other methods, of using a detailed QM description of the solute properties, allowing a description of effects due to specificities of the solute charge distribution. 

Intermolecular relaxation effects are a central issue in the interpretation of the ultraviolet photoelectron spectroscopy (UPS) of molecular solids. These relaxation effects result in several significant characteristics of UPS valence spectra, intermolecular relaxation phenomena lead to localized electron molecular-ion states, which are responsible for rigid gas-to-solid molecular spectral energy shifts, spectral line broadening, and dynamic electronic localization effects in aromatic pendant group polymers. 

Any techniqne that is sensitive to one or another of the reactant or prodnct species may be employed. For relatively slow reactions (reaction lifetimes longer than a few ms), simple spectrophotometric, electrochemical, magnetic resonance, and so on techniqnes may be employed. In order to make nseful determinations, the time for mixing the reactants and the instrumental response time must both be short compared to the reaction half-life (for a bimolecnlar reaction, t ji = >d.(i9l KpJ(.e excess reactant ). Reactions with shorter lifetimes (10 s > ti/2 > 10 s) can often be determined by spectral line broadening techniques at equilibrium, or by the... 

I was involved with both early on. In the case of transition-state spectroscopy, we had the idea that we could see the very short-lived intermediate between reagents and products by means of something like line broadening. The spectral line broadening would be due to the strong repulsion for a millionth of a millionth of a second seconds) between the pair of... 

---