MCQDT and close-coupled theory of non-Lorentzian line shapes in the predissociation of the O2 Schumann-Runge bands

1990 ◽  
Author(s):  
L. L. Vahala ◽  
P. S. Julienne ◽  
F. H. Mies
Keyword(s):  
Lorentzian Line ◽  
Line Shapes ◽  
Coupled Theory

Averaging of products of Lorentzian line shapes over thermal velocities

1968 ◽  
Vol 4 (7) ◽  
pp. 468-469 ◽  
Author(s):  
C. Heer ◽  
R. Settles ◽  
J. Bupp
Keyword(s):  
Lorentzian Line ◽  
Line Shapes

Broadening and shifting of the Raman Q branch in D2 and D2–He mixtures, II: line shapes, fitting routines, and effects nonlinear in density

1994 ◽  
Vol 72 (11-12) ◽  
pp. 891-896 ◽  
Author(s):  
P. M. Sinclair ◽  
P. Duggan ◽  
J. W. Forsman ◽  
J. R. Drummond ◽  
A. D. May
Keyword(s):  
Molecular Dynamics ◽  
Line Shape ◽  
Preceding Paper ◽  
Binary Collision ◽  
Spectral Profile ◽  
Lorentzian Line ◽  
Line Shapes ◽  
And Shifts ◽  
Three Body ◽  
First Time

In the preceding paper we fitted the experimental profiles using a single Lorentzian line shape and assumed that the width and shift were proportional to the density. Here we discuss nonlinear contributions to widths and shifts and present a different spectral profile and analysis that allows us (i) to determine unbiased, binary collision, impact limit, broadening and shifting coefficients; (ii) to disentangle several effects nonlinear in the density; and, subsequently, (iii) to observe broadening and shifting arising purely from the correlation between perturbers and three-body interactions. This is a new avenue of research in molecular dynamics. In addition, measurements of the broadening of the depolarized part of the Q branch in D2 are reported for the first time.

scholarly journals Detection of thermodynamic “valley noise” in monolayer semiconductors: Access to intrinsic valley relaxation time scales

2019 ◽  
Vol 5 (3) ◽  
pp. eaau4899 ◽  
Author(s):  
M. Goryca ◽  
N. P. Wilson ◽  
P. Dey ◽  
X. Xu ◽  
S. A. Crooker
Keyword(s):  
Time Scales ◽  
Relaxation Times ◽  
External Perturbation ◽  
Transition Metal Dichalcogenide ◽  
Pump Probe ◽  
Lorentzian Line ◽  
Line Shapes ◽  
Quantitative Measurements ◽  
Two Dimensional Materials ◽  
Valley Polarization

Together with charge and spin, many novel two-dimensional materials also permit information to be encoded in an electron’s valley degree of freedom—that is, in particular momentum states in the material’s Brillouin zone. With a view toward valley-based (opto)electronic technologies, the intrinsic time scales of valley scattering are therefore of fundamental interest. Here, we demonstrate an entirely noise-based approach for exploring valley dynamics in monolayer transition-metal dichalcogenide semiconductors. Exploiting their valley-specific optical selection rules, we use optical Faraday rotation to passively detect the thermodynamic fluctuations of valley polarization in a Fermi sea of resident carriers. This spontaneous “valley noise” reveals narrow Lorentzian line shapes and, therefore, long exponentially-decaying intrinsic valley relaxation. Moreover, the noise signatures validate both the relaxation times and the spectral dependence of conventional (perturbative) pump-probe measurements. These results provide a viable route toward quantitative measurements of intrinsic valley dynamics, free from any external perturbation, pumping, or excitation.

Comparative analysis of electron-phonon relaxation in a semiconducting carbon nanotube and a PbSe quantum dot

2008 ◽  
Vol 80 (7) ◽  
pp. 1433-1448 ◽  
Author(s):  
Bradley F. Habenicht ◽  
Svetlana V. Kilina ◽  
Oleg V. Prezhdo
Keyword(s):  
Carbon Nanotube ◽  
Quantum Dot ◽  
Density Functional ◽  
Low Frequency ◽  
Electronic Energy ◽  
Relaxation Processes ◽  
Phonon Modes ◽  
Lorentzian Line ◽  
Line Shapes ◽  
Optical Modes

The key features of the phonon-induced relaxation of electronic excitations in the (7,0) zig-zag carbon nanotube (CNT) and the Pb16Se16 quantum dot (QD) are contrasted using a time-domain ab initio density functional theory (DFT) simulation. Upon excitation from the valence to the conduction band (CB), the electrons and holes nonradiatively decay to the band-edge in both materials. The paper compares the electronic structure, optical spectra, important phonon modes, and decay channels in the CNT and QD. The relaxation is faster in the CNT than in the QD. In the PbSe QD, the electronic energy decays by coupling to low-frequency acoustic modes. The decay is nonexponential, in agreement with non-Lorentzian line-shapes observed in optical experiments. In contrast to the QD, the excitation decay in the CNT occurs primarily via high-frequency optical modes. Even though the holes have a higher density of states (DOS), they relax more slowly than the electrons, due to better coupling to low-frequency vibrations. Further, the expected phonon bottleneck is not observed in the QD, as rationalized by a high density of optically dark states. The same argument applies to the CNT. The computed results agree well with experimentally measured ultrafast relaxation time-scales and provide a unique atomistic picture of the electron-phonon relaxation processes.

Non-Lorentzian line shapes for interfering rotational resonances in the predissociation ofO2

1997 ◽  
Vol 55 (6) ◽  
pp. 4164-4167 ◽  
Author(s):  
B. R. Lewis ◽  
P. M. Dooley ◽  
J. P. England ◽  
S. T. Gibson ◽  
K. G. H. Baldwin ◽  
...  
Keyword(s):  
Lorentzian Line ◽  
Line Shapes

A Simple Numerical Method for Calculating Gaussian NMR Spectral Line Shapes Partially Narrowed Due to a Motion with the Exponential Spectral Autocorrelation Function

2002 ◽  
Vol 67 (4) ◽  
pp. 405-428 ◽  
Author(s):  
Jaromír Jakeš
Keyword(s):  
Spectral Line ◽  
Numerical Method ◽  
Autocorrelation Function ◽  
Intensity Increase ◽  
Central Intensity ◽  
Simple Modification ◽  
Second Moment ◽  
Lorentzian Line ◽  
Line Shapes ◽  
Gaussian Line

A simple numerical method for calculating NMR spectral line shapes resulting from a Gaussian line by a partial narrowing due to a motion with the exponential spectral autocorrelation function of the form exp (-|τ|/τc) was developed. It was found that the partially narrowed line is narrower not only than the parent Gaussian line with the second moment of ωp2 but also than the Lorentzian line with the half-width of 2ωp2τc obtained from the extreme narrowing approximation. The central intensity increase compared with the closer of these two lines is less than 50.2%. Asymptotic developments for large values of ω - ω0 and for large values of ωpτc were derived. Two-term approximation applied to the extreme narrowing case led to a very simple modification of the Lorentzian line having the correct second moment ωp2. Analysis of this modified Lorentzian line showed that attempts to estimate ωp2 from truncated second moments of Lorentzian lines without knowledge of τc are hopeless. The case of the polyexponential spectral autocorrelation function with all but one correlation times fast enough to allow for the extreme narrowing, modelling the case of an anisotropic motion, is also considered.

scholarly journals An R-Package for the Deconvolution and Integration of 1D NMR Data: MetaboDecon1D

Metabolites ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 452
Author(s):  
Martina Häckl ◽  
Philipp Tauber ◽  
Frank Schweda ◽  
Helena U. Zacharias ◽  
Michael Altenbuchinger ◽  
...  
Keyword(s):  
Biological Sample ◽  
Biological Fluids ◽  
Quantitative Description ◽  
R Package ◽  
Quantitative Information ◽  
Signal Identification ◽  
One Dimensional ◽  
Lorentzian Line ◽  
Line Shapes ◽  
Nmr Data

NMR spectroscopy is a widely used method for the detection and quantification of metabolites in complex biological fluids. However, the large number of metabolites present in a biological sample such as urine or plasma leads to considerable signal overlap in one-dimensional NMR spectra, which in turn hampers both signal identification and quantification. As a consequence, we have developed an easy to use R-package that allows the fully automated deconvolution of overlapping signals in the underlying Lorentzian line-shapes. We show that precise integral values are computed, which are required to obtain both relative and absolute quantitative information. The algorithm is independent of any knowledge of the corresponding metabolites, which also allows the quantitative description of features of yet unknown identity.

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