Line shifts

Line shifts as a function of pressure have been studied for pentacene and terrylene in /i-teriDhenyl [98, 99]. Botli exhibited linear and reversible spectral red shifts witli increasing pressure. Modest variations (factors of 1.3-1.6) in tlie pressure shifts among molecules were attributed to slightly different local environments. 

The term electrochromism was apparently coined to describe absorption line shifts induced in dyes by strong electric fields (1). This definition of electrocbromism does not, however, fit within the modem sense of the word. Electrochromism is a reversible and visible change in transmittance and/or reflectance that is associated with an electrochemicaHy induced oxidation—reduction reaction. This optical change is effected by a small electric current at low d-c potential. The potential is usually on the order of 1 V, and the electrochromic material sometimes exhibits good open-circuit memory. Unlike the well-known electrolytic coloration in alkaU haUde crystals, the electrochromic optical density change is often appreciable at ordinary temperatures. 

S.M. Sharma and Y.M. Gupta, Theoretical Analysis of R-Line Shifts of Ruby Subjected to Different Deformation Conditions. Accepted for publication, Phys. Rev. B (1990). 

Stress in crystalline solids produces small shifts, typically a few wavenumbers, in the Raman lines that sometimes are accompanied by a small amount of line broadening. Measurement of a series of Raman spectra in high-pressure equipment under static or uniaxial pressure allows the line shifts to be calibrated in terms of stress level. This information can be used to characterize built-in stress in thin films, along grain boundaries, and in thermally stressed materials. Microfocus spectra can be obtained from crack tips in ceramic material and by a careful spatial mapping along and across the crack estimates can be obtained of the stress fields around the crack. ... 

E is an error matrix taking errors of measurement (e. g. random noise) into consideration. The term component describes such chemical or physical states the spectra of which cannot be generated by a linear combination of the other components. Thus, components can be elements, chemical compounds - stoichiometric or non-stoichiometric - or even states induced by physical processes, provided that the spectra differ significantly, e. g. in line shapes or line shifts. 

Changes in relative peak intensity and marginal line shifts have been observed for benzene adsorbed on porous glass (26). More significantly, infrared spectroscopic evidence had been found in the appearance of inactive fundamentals for the lowering of molecular symmetry of benzene on adsorption on zeolites (47). 

Having included line shifts in the component frequencies, it can be regarded that Im f(0) = 0 and the asymptotic expansion of the denominator... 

Figure 5.16c indicates that as the channel size was reduced to Jh = 0.866 mm, the dispersed bubbly flow pattern vanished from the flow regime map. Figure 5.16a-c indicates that the slug-churn flow transition line shifted to the right, as the channel size was reduced. Similar trends were also found in small circular tubes by the... 

Other defects should be considered, such as uniform strain, which causes isotropic contraction/expan-sion of the cell giving rise to diffraction line shifts (but not broadening), chemical and/or phase segregation and... 

Distinct quadrupole shifts do occur as well in magnetically split spectra of single-crystals, poly crystalline powder or frozen solution samples. In all three cases, the line shifts obey the simple first-order expression at high-field condition. 

In the past two decades, 129Xe NMR has been employed as a useful technique for the characterization of the internal void space of nanoporous materials. In particular, the xenon chemical shift has been demonstrated to be very sensitive to the local environment of the nuclei and to depend strongly on the pore size and also on the pressure [4—6], Assuming a macroscopic inhomogeneity resulting from a distribution of adsorption site concentrations, 129Xe NMR spectra of xenon in zeolites have been calculated, and properties such as line widths, shapes as well as their dependence on xenon pressure can be reproduced qualitatively. A fully quantitative analysis, however, remains difficult due to the different contributions to the xenon line shift. (See Chapter 5.3 for a more detailed description of Xe spectroscopy for the characterization of porous media.)... 

The combination of microscopic and macroscopic information is made possible by what can be called parameter imaging . In the general sense, it consists of the encoding of properties such as spectral line shifts, relaxation times, diffusion coefficients, etc., in the image by suitable combination of corresponding modules into one pulse sequence. Parameter images are to be distinguished from mere... 

Moreover, the straight line shifts upward with an increase of Z. Thus, it is concluded that J oc Jo increases with an increase of Z for any AT. 

In the pivotal Chapter 4, temperature dependences of spectral line shifts and widths are analyzed. To treat them, we have to invoke rather complex concepts of... 

Temperature dependences of spectral line shifts and widths... 

The theory developed permits spectral line shift and width to be calculated from Taylor power series for interatomic potential energies in a concrete system. Various methods of tackling this problem can be found in the literature140,169,171,176 180 (see also survey 181 and references cited therein). Here we invoke a realistic model for the coupling of two mutually perpendicular vibrations which was reported by Burke, Langreth, Persson, and Zhang.1 As in Ref. 1, write the Hamiltonian for the interaction between the modes uh and w, in polar coordinates r and 6, where 6 is the angle between the adsorbate bond and the perpendicular to the surface plane ... 

In the framework of the low-temperature dephasing model, the dependence of spectral line shifts and widths for local vibrations on real dispersion laws for high-frequency (Qk) and low-frequency (a ) molecular modes is defined by the complex function (see Appendix 3) 184... 

Owing to the additional parameter Aa that enters into the above expression, the sign of ReFk is opposite to that of AQ k at Ao> k 2 > AQ k 2 + if. This fact proves to be fundamentally important in the analysis of temperature dependences of the spectral line shifts for the system CO/NaCl(100). 

Be NMR spectra are often referenced to aqueous beryllium sulfate as an external standard. Unfortunately, many workers using the standard appear to be unaware that the frequency of the observed line shifts to higher field with increasing concentration of sol-... 

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