Spectrum inhomogeneously broadened

Cavanagh MC, Martini IB, Schwartz BJ. (2004) Revisiting the pump-probe polarized transient hole-burning of the hydrated electron Is its absorption spectrum inhomogeneously broadened Chem Phys Letts 396 359-366. 

However, its qualitative difference from the spectrum obtained in the col-lisional model is that it is inhomogeneously broadened and its structure may be observed in a nonlinear optical experiment. 

N. Steigerwald, M. L. and Brus, L. E. (1988) Electronic states of semiconductor clusters - homogeneous and inhomogeneous broadening ofthe optical-spectrum./. Chem. Phys., 89, 4001 1011. 

Initial position of instant spectrum of fluorescence and character of spectral shifts in time depend on the excitation frequency, i.e., inhomogeneous broadening is of dynamic nature as a degree of broadening is maximal at the initial instants of time and decreases with time of emission registration (demonstration in panel d of Fig. 5). 

FIGURE 4.2 Linewidth increase with temperature for an S = 1/2 system. The linewidth of a feature in the low-spin heme spectrum from cytochrome a in bovine heart cytochrome oxidase has been fit as a convolution of a constant component from inhomogeneous broadening and a temperature-dependent component from homogeneous broadening (Hagen 2006). (Reproduced by permission of The Royal Society of Chemistry.)... 

The width of a band in the absorption spectrum of a chromophore located in a particular microenvironment is a result of two effects homogeneous and inhomogeneous broadening. Homogeneous broadening is due to the existence of a continuous set of vibrational sublevels in each electronic state. Inhomogeneous broadening results from the fluctuations of the structure of the solvation shell... 

Site-selection spectroscopy Maximum selectivity in frozen solutions or vapor-deposited matrices is achieved by using exciting light whose bandwidth (0.01-0.1 cm-1) is less than that of the inhomogeneously broadened absorption band. Lasers are optimal in this respect. The spectral bandwidths can then be minimized by selective excitation only of those fluorophores that are located in very similar matrix sites. The temperature should be very low (5 K or less). The techniques based on this principle are called in the literature site-selection spectroscopy, fluorescence line narrowing or energy-selection spectroscopy. The solvent (3-methylpentane, ethanol-methanol mixtures, EPA (mixture of ethanol, isopentane and diethyl ether)) should form a clear glass in order to avoid distortion of the spectrum by scatter from cracks. 

Section 3.5.1 described the various effects observed upon excitation at the red-edge of the absorption spectrum. In particular, a lack of energy transfer was first observed by G. Weber (1960) (and is called Weber s effect for this reason). This effect can be explained in terms of inhomogeneous broadening of spectra. In a rigid polar solution of fluorophores that are close enough to undergo non-radiative en-... 

An example of an inhomogeneously broadened peak is found for CO physisorbed on an Al(lOO) surface. In addition to the dipole-dipole coupling there is a substantial short range interaction. The adsorbed molecules do not form any ordered structures and hence the overlayer contains a large degree of disorder. We find in Fig. 10 a spectrum with a rather Gaussian shaped peak with a high frequency tail. However, as the structure of this system is unknown it s not possible to make a more detailed interpretation of the peak shape. 

Recently, an ESR spectrum from Aujj at 4.4 K, with g= 1.9204 and linewidth 67 mT, has been reported [54]. The intensity of the signal followed the Curie-Weiss law, and the g-value and linewidth were independent of temperature. If the linewidth were determined by the electronic spin-spin relaxation time Tj, it would be expected to increase with temperature, so its temperature-independence suggests inhomogeneous broadening by unresolved hyperfine coupling to P and Au nuclei. Similar behaviour has been found in rhodium carbonyl clusters [18]. 

There are a large number of cases where the spectra of luminescence centers remain broad up to helium temperatures. In certain cases, this is explained by a strong electron-phonon interaction, but more often the inhomogeneous broadening, connected with several types of the same center presence, causes this. In such cases it is possible to simplify the spectrum by selective excitation of specific centers. 

Molecules in crystals or dispersed in host lattices are often present in a range of environments, and this results in a broadening of the electronic absorption spectrum. Such an inhomogeneously broadened absorption band (envelope of transitions) may be considered as a superposition of several distinguishable sites. A narrow line laser can saturate one of the transitions under the envelope and the corresponding molecules will no longer take part in the absorption process. This phenomenon is referred to as hole... 

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