Spectral line shift

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... 

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). 

Table 8 Spectral line shifts (in nm) of alkali atoms embedded in liquid helium. Experimental values are presented together with relativistic RLDA as well as other nonrelativistic (NR) results...

Finally, we note that ultracold hydrogen holds enormous potential for the study of atomic interactions. For instance, scattering lengths can be determined directly from spectral line shifts [8]. Furthermore, photoassociation spectroscopy can be used to investigate the potentials for excited H% potentials, as in a recent investigation of the molecular triplet a317+ potential [13],... 

Absorption and fluorescence experiments observe the solvatochromic shift of molecular (usually electronic) transitions. Several authors have reported similar density dependences for the shift of fluorescence or absorbance spectral lines in different solute/SCF solvent systems (31-33). This density dependence is characterized by three regions. At low densities, the absorption/emission line red shifts strongly with density. Around pc/2, the slope changes and the line position becomes approximately independent of density. At higher densities, somewhat above pc, the slope changes again, and the spectral line shifts further to the red with increasing density. 

Lanthanides have isotopes which may used in this technique. The principle consists of measuring resonant y-ray absorption as a function of relative velocity between the source and the sample. The spectral line shifts and splittings give information on the chemical nature and symmetry of the site of ion. Eu3+-transferrin [53] and tumor metabolism studies [54] with 153Sm have not proved to be particularly informative. 

Moseley labored on. He had trouble at fi rst making sharp photographs of his X-ray spectra, but once he got the hang of it the results were outstanding. The important spectral lines shifted with absolute regularity as he... 

It is good experimental practice to run a qualitative scan on any sample submitted for quantitative analysis in order to uncover potential overlap and other interference problems. In order to scan the entire wavelength (0.2-20 A), it is necessary to utilize several crystals and two detectors. The scanning speed [degrees (2 ) per minute] and time constant must be chosen so as not to introduce spectral line shifting... 

Recent advances in experimental investigations on spectral line shifts of foreign atoms in liquid helium environments [1-7] and their interpretations... 

SBM is a relatively crude approximation and usually gives only an overall estimate of spectral line shifts without giving any detailed information about transition properties. Nevertheless, it gives in many cases a reasonable estimate of spectral line shifts [2, 18, 41]. 

A systematic approach which gives a simple interpretation of the spectral line shifts and of other structural properties of spectra of foreign atoms surrounded by liquid helium has been presented. Results for hydrogen and helium atoms show that the qualitative behaviour of the calculated spectral properties agrees with experimentally available data. No specific experimen-... 

Most of the lanthanides have isotopes suitable for Mossbauer spectroscopy, c/., e.g., Wertheim (1964). In such experiments the resonant y-ray absorption is measured as a function of the relative velocity between the source and the sample. Spectral line shifts and splittings are related to the chemical nature and symmetry of the site of the ion. Spartalian and Oosterhuis (1973) have examined the spectrum of the Eu -transferrin complex. A single unshifted line was observed, which by itself offers little information. This is because at the low temperature (4.2 K) at which such experiments are normally carried out, only the ground-singlet level, of Eu is populated and it is hardly affected by the environment. Mossbauer spectra of other members of the lanthanide series should be more informative. 

Finally, we have obtained spectra of / -trialanine of varying crystal quality. By comparing the spectrum from an annealed sample (originally of poor crystal quality) with the spectrum of another poor quality sample exposed to vacuum to remove any trace water, it was shown that line broadening and some spectral line shifts can be attributed to crystal defects rather than the presence of water. Overall, we have shown the extreme sensitivity of THz spectra to intermolecular interactions including variations in the level of hydration, hydrophobic interactions between solvent and peptide and the presence of crystal defects. 

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