Pressure line broadening

The spectral line width is mainly determined by the Doppler and pressure line broadening effects, and the total line broadening (Avj-) may be written... 

Carbon Dioxide The contribution to the emissivity of a gas containing CO9 depends on gas temperature Tc, on the CO9 partial pressure-beam length product p L and, to a much lesser extent, on the total pressure P. Constants for use in evaluating at a total pressure of 101.3 kPa (1 atm) are given in Table 5-8 (more on this later). The gas absorptivity Ot equals the emissivity when the absorbing gas and the emitter are at the same temperature. When the emitter surface temperature is Ti, Ot is (Tc/Ti)° times , evaluated using Table 5-8 at T instead of Tc and at p LTi/Tc instead of Line broadening, due to... 

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. ... 

The effect of a pressure of 80 and 150 MPa on the spin-state transition has been also studied [169], a series of spectra obtained at 150 MPa being shown in Fig. 32. The speetra show relaxation effects as line broadening and linewidth asymmetry. Calculated spectra were obtained in the same way as at ambient pressure. Rate constants for a number of temperatures are listed in Table 12, the parameter values resulting from an Arrhenius plot of the rate constants being listed in Table 13. In Fig. 33, the quantity 5g of Eq. (36) has been plotted as a... 

DR. SWADDLE Yes, that is correct. As I stated, we have been careful to work in areas where at least 90 percent of the line broadening is controlled by solvent exchange. I think John Hunt is the person to comment on what happens to the other NMR parameters under pressure. I believe he has found some pressure-dependence of T. ... 

The aqua ion is not easily reduced nor oxidized. It is the slowest reacting of the bivalent transition metal ions with e " k = 7.7 X 10 M s ) and the product Mn+q is very reactive. However Mn(CNR)5 (R = a variety of alkyl and aryl groups) is stable and the selfexchange in the Mn(l,ll) hexakis(isocyanide) system has been studied by Mn and H nmr line broadening. The effects of solvent, temperature, pressure and ligand have been thoroughly explored. 

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. 

In the specific case of the tailed sapphyrin carboxylates 5 and 6, for which evidence of self-assembly was noted in the solid state (vide supra), H NMR spectroscopic studies carried out in 4-methanol, d-chloroform, and mixtures of the two solvents showed strong line broadening, and upfield shifts of the methylene tail peaks. Such findings are, of course, fully consistent with the proposed dimerization. Further, dilution experiments performed over a concentration range of 50 to 5 mM in these solvents showed little change in the spectra, indicating that the dimeric form prevails under these conditions, even in highly polar solvents. In the case of 6, the actual dimeric stoichiometry was confirmed by vapor pressure osmometry (VPO) measurements carried out in 1,2-dichloroethane. 

Doppler and pressure effects broaden the atomic lines by one to two orders of magnitude relative to their inherent linewidths. 

The most important source of line broadening in microwave studies of bulk gas samples is collisional or pressure broadening, the theory of which was first developed by Van Vleck and Weisskopf [77], They developed the line shape function... 

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