scholarly journals Temperature Dependence of Raman Frequency Shift in SrWO4 Crystal Studied by Lattice Dynamical Calculations

Crystals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 197 ◽  
Author(s):  
Jun Suda ◽  
Petr Zverev
Keyword(s):  
Frequency Shift ◽  
Temperature Dependence ◽  
Temperature Shift ◽  
Order Perturbation ◽  
Perturbative Approach ◽  
First Order ◽  
Experimental Temperature Dependence ◽  
Raman Lasers ◽  
Anharmonic Term ◽  
Raman Modes

The frequency shift of the Raman modes in strontium tungstate (SrWO4) was investigated in the temperature range from 15 to 295 K. The experimental temperature dependence of the shift was analyzed using both the lattice dynamical calculations and the lattice perturbative approach. We found that the quartic anharmonic term of the first-order perturbation and the cubic term of the second-order perturbation, as well as the thermal expansion, contribute to the temperature shift of the highest-frequency Ag(ν1) mode. The values of the temperature sensitivity of the frequency shift of the Raman modes at room temperature were measured, which is important for developing high-power crystalline Raman lasers and frequency shifters.

scholarly journals Anharmonic Lattice Vibrations and the Temperature Shift of Raman Spectral Lines

1996 ◽  
Vol 51 (5-6) ◽  
pp. 716-720 ◽  
Author(s):  
Christovam Mendonça ◽  
Said R. Rabbani
Keyword(s):  
Temperature Dependence ◽  
Coupled Oscillators ◽  
Temperature Shift ◽  
Spectral Lines ◽  
Anharmonic Lattice ◽  
Lattice Mode ◽  
Anharmonic Term ◽  
Librational Motion ◽  
Average Lattice ◽  
Raman Spectral

Abstract The temperature dependence of the average lattice mode frequency of a molecule undergoing librational motion in a quasi-harmonic potential has been calculated with the purpose of finding an explicit relationship between the observed shift of Raman spectral lines with temperature and the anharmonic term in the rotational potential. Calculations were carried out both for uncoupled and coupled oscillators. The equations obtained with this model provide good fittings for solid Cl2 and benzene data. This result can be applied to the analysis of the temperature dependence of NQR frequencies in molecular crystals.

Temperature Dependent Phononic Response of Few Layered MoS2 Nanosheets

2018 ◽  
Vol 4 (5) ◽  
pp. 546-548
Author(s):  
Sneha Sinha ◽  
Vasant Sathe ◽  
Sunil K. Arora
Keyword(s):  
Temperature Dependence ◽  
Phonon Scattering ◽  
Linear Temperature Dependence ◽  
Mos2 Nanosheets ◽  
Temperature Dependent ◽  
Linear Temperature ◽  
First Order ◽  
Non Linear ◽  
Out Of Plane ◽  
Raman Modes

From the temperature dependent phononic studies of few layered liquid phase exfoliated MoS2 nanosheets we find that the E12g (in-plane) and A1g (out-of-plane) Raman modes follow red shift with increase in temperature and exhibits non-linear temperature dependence in the entire temperature range (80 to 600 K). The first-order temperature coefficients for E12g and A1g modes are found to be -0.0133 cm-1K-1 and -0.0092 cm-1K-1, respectively. The physical origin of the non-linear temperature dependence is analyzed using an analytical model that includes contribution of the thermal expansion and an-harmonic effects to the lattice potential. Our analysis suggests that the non-linear temperature dependence of E12g and A1g modes mainly originates from the an-harmonic contributions from three-phonon and four-phonon scattering.

scholarly journals Theoretical uncertainties for cosmological first-order phase transitions

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Djuna Croon ◽  
Oliver Gould ◽  
Philipp Schicho ◽  
Tuomas V. I. Tenkanen ◽  
Graham White
Keyword(s):  
Phase Transitions ◽  
Standard Model ◽  
Scale Dependence ◽  
Effective Field ◽  
Bubble Nucleation ◽  
Perturbative Approach ◽  
First Order ◽  
The Standard Model ◽  
First Order Phase ◽  
Renormalisation Scale

Abstract We critically examine the magnitude of theoretical uncertainties in perturbative calculations of fist-order phase transitions, using the Standard Model effective field theory as our guide. In the usual daisy-resummed approach, we find large uncertainties due to renormalisation scale dependence, which amount to two to three orders-of-magnitude uncertainty in the peak gravitational wave amplitude, relevant to experiments such as LISA. Alternatively, utilising dimensional reduction in a more sophisticated perturbative approach drastically reduces this scale dependence, pushing it to higher orders. Further, this approach resolves other thorny problems with daisy resummation: it is gauge invariant which is explicitly demonstrated for the Standard Model, and avoids an uncontrolled derivative expansion in the bubble nucleation rate.

scholarly journals Perturbation Solution for One-Dimensional Flow to a Constant-Pressure Boundary in a Stress-Sensitive Reservoir

2021 ◽  
Author(s):  
Amarjot Singh Bhullar ◽  
Gospel Ezekiel Stewart ◽  
Robert W. Zimmerman
Keyword(s):  
Approximate Solution ◽  
Pore Pressure ◽  
Constant Pressure ◽  
Initial Permeability ◽  
Order Perturbation ◽  
Zeroth Order ◽  
One Dimensional ◽  
First Order ◽  
Outflow Boundary ◽  
Perturbation Solutions

Abstract Most analyses of fluid flow in porous media are conducted under the assumption that the permeability is constant. In some “stress-sensitive” rock formations, however, the variation of permeability with pore fluid pressure is sufficiently large that it needs to be accounted for in the analysis. Accounting for the variation of permeability with pore pressure renders the pressure diffusion equation nonlinear and not amenable to exact analytical solutions. In this paper, the regular perturbation approach is used to develop an approximate solution to the problem of flow to a linear constant-pressure boundary, in a formation whose permeability varies exponentially with pore pressure. The perturbation parameter αD is defined to be the natural logarithm of the ratio of the initial permeability to the permeability at the outflow boundary. The zeroth-order and first-order perturbation solutions are computed, from which the flux at the outflow boundary is found. An effective permeability is then determined such that, when inserted into the analytical solution for the mathematically linear problem, it yields a flux that is exact to at least first order in αD. When compared to numerical solutions of the problem, the result has 5% accuracy out to values of αD of about 2—a much larger range of accuracy than is usually achieved in similar problems. Finally, an explanation is given of why the change of variables proposed by Kikani and Pedrosa, which leads to highly accurate zeroth-order perturbation solutions in radial flow problems, does not yield an accurate result for one-dimensional flow. Article Highlights Approximate solution for flow to a constant-pressure boundary in a porous medium whose permeability varies exponentially with pressure. The predicted flowrate is accurate to within 5% for a wide range of permeability variations. If permeability at boundary is 30% less than initial permeability, flowrate will be 10% less than predicted by constant-permeability model.

A kinetic standard for precise calibration of spectrophotometer cell temperature.

1981 ◽  
Vol 27 (5) ◽  
pp. 753-755 ◽  
Author(s):  
P A Adams ◽  
M C Berman
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cell Temperature ◽  
First Order ◽  
Order Rate ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

Abstract We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).

35Cl NQR Spectroscopy on Salts and Molecular Compounds of Trichloroacetic Acid

1986 ◽  
Vol 41 (1-2) ◽  
pp. 215-224 ◽  
Author(s):  
Winfried Fichtner ◽  
Axel Markworth ◽  
Norbert Weiden ◽  
Alarich Weiss
Keyword(s):  
Frequency Shift ◽  
Temperature Dependence ◽  
Linear Relation ◽  
Trichloroacetic Acid ◽  
Mean Frequency ◽  
35Cl Nqr ◽  
The Mean ◽  
Molecular Compounds

The temperature dependence of salts M(1)H(Cl3CCOO)2 and molecular compounds of trichloroacetic acid with amines and benzaldehydes, TCA · X, was studied,The data fit rather well to the known dependence of the mean frequency shift Δ <v(35Cl)> on the pkadifference of X with respect to TCA. A linear relation is observed between the bleaching out temperature Tb of the 35Cl NQR lines and Δ <v(35Cl)> for M(1)H(Cl3CCOO)2 and for TCA · X, X = benzaldehydes.

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