Raman study of pressure effects on frequencies and isotropic line shapes in liquid acetone

1982 ◽  
Vol 76 (7) ◽  
pp. 3493-3496 ◽  
Author(s):  
W. Schindler ◽  
P. T. Sharko ◽  
J. Jonas
Keyword(s):  
Pressure Effects ◽  
Line Shapes ◽  
Isotropic Line ◽  
Raman Study ◽  
Liquid Acetone

scholarly journals Pressure effects on water vapour lines: beyond the Voigt profile

2012 ◽  
Vol 370 (1968) ◽  
pp. 2495-2508 ◽  
Author(s):  
N. H. Ngo ◽  
H. Tran ◽  
R. R. Gamache ◽  
J. M. Hartmann
Keyword(s):  
Water Vapour ◽  
Line Shape ◽  
Pressure Effects ◽  
Shape Model ◽  
Line Shapes ◽  
Voigt Profile ◽  
Voigt Model ◽  
Velocity Changes ◽  
Dynamics Simulations ◽  
Induced Velocity

A short overview of recent results on the effects of pressure (collisions) regarding the shape of isolated infrared lines of water vapour is presented. The first part of this study considers the basic collisional quantities, which are the pressure-broadening and -shifting coefficients, central parameters of the Lorentzian (and Voigt) profile and thus of any sophisticated line-shape model. Through comparisons of measured values with semi-classical calculations, the influences of the molecular states (both rotational and vibrational) involved and of the temperature are analysed. This shows the relatively unusual behaviour of H 2 O broadening, with evidence of a significant vibrational dependence and the fact that the broadening coefficient (in cm −1 atm −1 ) of some lines increases with temperature. In the second part of this study, line shapes beyond the Voigt model are considered, thus now taking ‘velocity effects’ into account. These include both the influence of collisionally induced velocity changes that lead to the so-called Dicke narrowing and the influence of the dependence of collisional parameters on the speed of the radiating molecule. Experimental evidence of deviations from the Voigt shape is presented and analysed. The interest of classical molecular dynamics simulations, to model velocity changes, together with semi-classical calculations of the speed-dependent collisional parameters for line-shape predictions from ‘first principles’, are discussed.

scholarly journals Recommended isolated-line profile for representing high-resolution spectroscopic transitions (IUPAC Technical Report)

2014 ◽  
Vol 86 (12) ◽  
pp. 1931-1943 ◽  
Author(s):  
Jonathan Tennyson ◽  
Peter F. Bernath ◽  
Alain Campargue ◽  
Attila G. Császár ◽  
Ludovic Daumont ◽  
...  
Keyword(s):  
High Resolution ◽  
Line Profile ◽  
Pressure Effects ◽  
Task Group ◽  
High Resolution Spectroscopy ◽  
Line Shapes ◽  
Neutral Gas ◽  
Voigt Profile ◽  
Simplifying Assumptions ◽  
On Line

Abstract The report of an IUPAC Task Group, formed in 2011 on “Intensities and line shapes in high-resolution spectra of water isotopologues from experiment and theory” (Project No. 2011-022-2-100), on line profiles of isolated high-resolution rotational-vibrational transitions perturbed by neutral gas-phase molecules is presented. The well-documented inadequacies of the Voigt profile (VP), used almost universally by databases and radiative-transfer codes, to represent pressure effects and Doppler broadening in isolated vibrational-rotational and pure rotational transitions of the water molecule have resulted in the development of a variety of alternative line-profile models. These models capture more of the physics of the influence of pressure on line shapes but, in general, at the price of greater complexity. The Task Group recommends that the partially Correlated quadratic-Speed-Dependent Hard-Collision profile (pCqSD-HCP) should be adopted as the appropriate model for high-resolution spectroscopy. For simplicity this should be called the Hartmann–Tran profile (HTP). The HTP is sophisticated enough to capture the various collisional contributions to the isolated line shape, can be computed in a straightforward and rapid manner, and reduces to simpler profiles, including the Voigt profile, under certain simplifying assumptions.

Line-Shape Analyses of Solid-state 17O NMR Spectra for Hexagonal Ice

2014 ◽  
Vol 69 (7) ◽  
pp. 786-792 ◽  
Author(s):  
Kazuhiko Yamada ◽  
Kenzo Deguchi ◽  
Tadashi Shimizu ◽  
Junji Watanabe
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
17O Nmr ◽  
Line Shapes ◽  
Quadrupole Interactions ◽  
Isotropic Line ◽  
Hexagonal Ice ◽  
Theoretical Investigations ◽  
Proton Disorder ◽  
Shape Analyses

We present the results of experimental and theoretical investigations of line shapes in solid-state 17O NMR spectra of hexagonal ice, Ih. Stationary 17O NMR spectra of Ih at temperatures from 143 to 280 K were obtained at 11.7 and 16.4 T. Line shapes changed drastically as the temperature was increased from 143 to 243 K; at 253 K and above, pseudo-isotropic line shapes appear, indicating the presence of reorientational motions. We find that Ratcliffe’s model, which involves twelve orientations and four-step jumps for water reorientational motions, is effective for analyzing the NMR spectra at temperatures below 243 K. The present analysis demonstrates that the isotropic line shapes arise from proton disorder with respect to the solid-state 17O NMR time scale, producing pseudoicosahedral motional averaging that can completely average out second-order quadrupole interactions.

Nonlinear Raman study of line shapes and relaxation of vibrational states of isotopically pure and mixed crystals of benzene

1984 ◽  
Vol 81 (11) ◽  
pp. 4746-4759 ◽  
Author(s):  
T. J. Trout ◽  
S. Velsko ◽  
R. Bozio ◽  
P. L. Decola ◽  
Robin M. Hochstrasser
Keyword(s):  
Mixed Crystals ◽  
Vibrational States ◽  
Line Shapes ◽  
Raman Study

Reduction in Pain Sensitivity from Pharmacological Elevation of Blood Pressure in Persons with Chronically Low Blood Pressure

2009 ◽  
Vol 23 (3) ◽  
pp. 104-112 ◽  
Author(s):  
Stefan Duschek ◽  
Heike Heiss ◽  
Boriana Buechner ◽  
Rainer Schandry
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Pain Sensitivity ◽  
Pain Threshold ◽  
Pain Perception ◽  
Drug Effects ◽  
Pressure Effects ◽  
Double Blind ◽  
Low Blood Pressure ◽  
Present Trial

Recent studies have revealed evidence for increased pain sensitivity in individuals with chronically low blood pressure. The present trial explored whether pain sensitivity can be reduced by pharmacological elevation of blood pressure. Effects of the sympathomimetic midodrine on threshold and tolerance to heat pain were examined in 52 hypotensive persons (mean blood pressure 96/61 mmHg) based on a randomized, placebo-controlled, double-blind design. Heat stimuli were applied to the forearm via a contact thermode. Confounding of drug effects on pain perception with changes in skin temperature, temperature sensitivity, and mood were statistically controlled for. Compared to placebo, higher pain threshold and tolerance, increased blood pressure, as well as reduced heart rate were observed under the sympathomimetic condition. Increases in systolic blood pressure between points of measurement correlated positively with increases in pain threshold and tolerance, and decreases in heart rate were associated with increases in pain threshold. The findings underline the causal role of hypotension in the augmented pain sensitivity related to this condition. Pain reduction as a function of heart rate decrease suggests involvement of a baroreceptor-related mechanism in the pain attrition. The increased proneness of persons with chronic hypotension toward clinical pain is discussed.

Sign in / Sign up

Export Citation Format

Share Document