The Stokes' Shift in Impurity Spectral Lines. II. Relationship to the Adiabatic Approximation Approach

1972 ◽  
Vol 50 (3) ◽  
pp. 231-236 ◽  
Author(s):  
Robert Barrie ◽  
I. W. Sharpe ◽  
B. L. Jones
Keyword(s):  
Canonical Transformation ◽  
Adiabatic Approximation ◽  
Stokes Shift ◽  
Spectral Lines ◽  
Approximation Approach ◽  
The Relationship

The derivation of the Stokes' shift has been performed without making the adiabatic approximation. A canonical transformation is used to show the relationship between that method and the more usual one in which the adiabatic approximation is made.

The Stokes' Shift in Impurity Spectral Lines. I. Mathematical Technique

1972 ◽  
Vol 50 (3) ◽  
pp. 222-230 ◽  
Author(s):  
Robert Barrie ◽  
I. W. Sharpe
Keyword(s):  
Adiabatic Approximation ◽  
Stokes Shift ◽  
Spectral Lines ◽  
New Method ◽  
Mathematical Technique ◽  
Impurity Site ◽  
Systematic Fashion

A new method of deriving the Stokes' shift in impurity spectral lines is presented. The adiabatic approximation is not used. The method makes use of the fact that at most one electron can be bound at the impurity site and reduces the problem in a systematic fashion to the evaluation of traces over only phonon states. A new method is given of evaluating these traces for a particular electron–phonon system which has the chief features required to discuss the Stokes' shift.

scholarly journals Epistatic contributions promote the unification of incompatible models of neutral molecular evolution

2020 ◽  
Vol 117 (11) ◽  
pp. 5873-5882 ◽  
Author(s):  
Jose Alberto de la Paz ◽  
Charisse M. Nartey ◽  
Monisha Yuvaraj ◽  
Faruck Morcos
Keyword(s):  
Structural Information ◽  
Stokes Shift ◽  
Neutral Evolution ◽  
Emergent Properties ◽  
Sequence Evolution ◽  
Sequence Alignments ◽  
Multiple Sequence ◽  
Multiple Sequence Alignments ◽  
Analysis Methodology ◽  
The Relationship

We introduce a model of amino acid sequence evolution that accounts for the statistical behavior of real sequences induced by epistatic interactions. We base the model dynamics on parameters derived from multiple sequence alignments analyzed by using direct coupling analysis methodology. Known statistical properties such as overdispersion, heterotachy, and gamma-distributed rate-across-sites are shown to be emergent properties of this model while being consistent with neutral evolution theory, thereby unifying observations from previously disjointed evolutionary models of sequences. The relationship between site restriction and heterotachy is characterized by tracking the effective alphabet dynamics of sites. We also observe an evolutionary Stokes shift in the fitness of sequences that have undergone evolution under our simulation. By analyzing the structural information of some proteins, we corroborate that the strongest Stokes shifts derive from sites that physically interact in networks near biochemically important regions. Perspectives on the implementation of our model in the context of the molecular clock are discussed.

scholarly journals Magnetic activity in the HARPS M dwarf sample

2017 ◽  
Vol 600 ◽  
pp. A13 ◽  
Author(s):  
N. Astudillo-Defru ◽  
X. Delfosse ◽  
X. Bonfils ◽  
T. Forveille ◽  
C. Lovis ◽  
...  
Keyword(s):  
Monitoring Program ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Spectral Lines ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
The Galaxy ◽  
Low Mass ◽  
M Dwarf ◽  
The Relationship

Context. Atmospheric magnetic fields in stars with convective envelopes heat stellar chromospheres, and thus increase the observed flux in the Ca ii H and K doublet. Starting with the historical Mount Wilson monitoring program, these two spectral lines have been widely used to trace stellar magnetic activity, and as a proxy for rotation period (Prot) and consequently for stellar age. Monitoring stellar activity has also become essential in filtering out false-positives due to magnetic activity in extra-solar planet surveys. The Ca ii emission is traditionally quantified through the R'HK-index, which compares the chromospheric flux in the doublet to the overall bolometric flux of the star. Much work has been done to characterize this index for FGK-dwarfs, but M dwarfs – the most numerous stars of the Galaxy – were left out of these analyses and no calibration of their Ca ii H and K emission to an R'HK exists to date. Aims. We set out to characterize the magnetic activity of the low- and very-low-mass stars by providing a calibration of the R'HK-index that extends to the realm of M dwarfs, and by evaluating the relationship between R'HK and the rotation period. Methods. We calibrated the bolometric and photospheric factors for M dwarfs to properly transform the S-index (which compares the flux in the Ca ii H and K lines to a close spectral continuum) into the R'HK. We monitored magnetic activity through the Ca ii H and K emission lines in the HARPS M dwarf sample. Results. The R'HK index, like the fractional X-ray luminosity LX/Lbol, shows a saturated correlation with rotation, with saturation setting in around a ten days rotation period. Above that period, slower rotators show weaker Ca ii activity, as expected. Under that period, the R'HK index saturates to approximately 10-4. Stellar mass modulates the Ca ii activity, with R'HK showing a constant basal activity above 0.6 M⊙ and then decreasing with mass between 0.6 M⊙ and the fully-convective limit of 0.35 M⊙. Short-term variability of the activity correlates with its mean level and stars with higher R'HK indexes show larger R'HK variability, as previously observed for earlier spectral types.

The Experiment Study on Flash Spectrum Produced by Hypervelocity Impact

2015 ◽  
Vol 782 ◽  
pp. 197-203
Author(s):  
Kai Zhang ◽  
Qing Ming Zhang ◽  
Ren Rong Long
Keyword(s):  
Space Debris ◽  
Hypervelocity Impact ◽  
Spectral Lines ◽  
Line Spectrum ◽  
Weapon System ◽  
Flash Intensity ◽  
System A ◽  
Flash Spectrum ◽  
The Relationship ◽  
Important Significance

It is an inevitable phenomenon that flash is generated in the process of hypervelocity impact. The research on impact flash is of important significance for assessing the collision between space debris and spacecraft, identifying the material properties on the surface of planet, evaluating the damage of weapon system. A measurement system was built in order to acquire flash spectrum ranging in wavelength from 200 to 1100nm. The relationship between flash intensity and impact velocity was studied. The spectrum consists of line spectrum and continuous spectrum. Line spectrum mainly concentrates in the range of 200-500nm. The spectral lines of the elements were identified. The strong flash happens within 2.2ms after beginning to impact. In addition, the electron temperature of plasma produced in hypervelocity impact is calculated by spectral method, and compared with the temperature measured by Langmuir three probes.

scholarly journals The Binarity of Early-type Stars from LAMOST Medium-resolution Spectroscopic Survey

2021 ◽  
Author(s):  
Yanjun Guo ◽  
Jiao Li ◽  
Jianping Xiong ◽  
Jiangdan Li ◽  
Luqian Wang ◽  
...  
Keyword(s):  
Orbital Period ◽  
Likelihood Estimation ◽  
Spectral Lines ◽  
Spectroscopic Binaries ◽  
Early Type ◽  
Mass Ratio ◽  
Medium Resolution ◽  
Early Type Stars ◽  
Relationship Of ◽  
The Relationship

Abstract Massive binaries play significant roles in many fields. Identification of massive stars, particularly massive binaries, is of great importance. In this paper, by adopting the technique of measuring the equivalent widths of several spectral lines, we identified 9,382 early-type stars from LAMOST medium-resolution survey and divided the sample into four groups, T1 ($\sim$O-B4), T2 ($\sim$B5), T3 ($\sim$B7), and T4 ($\sim$B8-A). The relative radial velocities $RV_{\rm rel}$ were calculated using the Maximum Likelihood Estimation. The stars with significant changes of $RV_{\rm rel}$ and at least larger than 15.57km s$^{-1}$ were identified as spectroscopic binaries. We found that the observed spectroscopic binary fractions for the four groups are $24.6\%\pm0.5\%$, $20.8\%\pm0.6\%$, $13.7\%\pm0.3\%$, and $7.4\%\pm0.3\%$, respectively. Assuming that orbital period ($P$) and mass ratio ($q$) have intrinsic distributions as $f(P) \propto P^\pi$ (1\textless$P$\textless1000 days) and $f(q) \propto q^\kappa$ (0.1\textless$q$\textless1), respectively, we conducted a series of Monte-Carlo simulations to correct observational biases for estimating the intrinsic multiplicity properties. The results show that the intrinsic binary fractions for the four groups are 68$\%\pm8\%$, 52$\%\pm3\%$, 44$\%\pm6\%$, and 44$\%\pm6\%$, respectively. The best estimated values for $\pi$ are -1$\pm0.1$, -1.1$\pm0.05$, -1.1$\pm0.1$, and -0.6$\pm0.05$, respectively. The $\kappa$ cannot be constrained for groups T1 and T2 and is -2.4$\pm0.3$ for group T3 and -1.6$\pm0.3$ for group T4. We confirmed the relationship of a decreasing trend in binary fractions towards late-type stars. No correlation between the spectral type and the orbital period distribution has been found yet, possibly due to the limitation of observational cadence.

scholarly journals The Generalization of the Poisson Sum Formula Associated with the Linear Canonical Transform

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Jun-Fang Zhang ◽  
Shou-Ping Hou
Keyword(s):  
Fourier Transform ◽  
Canonical Transformation ◽  
Linear Canonical Transform ◽  
Original Signal ◽  
Periodic Property ◽  
Sum Formula ◽  
The Relationship

The generalization of the classical Poisson sum formula, by replacing the ordinary Fourier transform by the canonical transformation, has been derived in the linear canonical transform sense. Firstly, a new sum formula of Chirp-periodic property has been introduced, and then the relationship between this new sum and the original signal is derived. Secondly, the generalization of the classical Poisson sum formula to the linear canonical transform sense has been obtained.

scholarly journals Determination and Study the Energy Characteristics of Vibrational-Rotational Levels and Spectral Lines of GaF, GaCl, GaBr and GaI for Ground State

2015 ◽  
Vol 50 ◽  
pp. 96-112
Author(s):  
Adil Nameh Ayaash
Keyword(s):  
Quantum Number ◽  
Computer Model ◽  
Ground State ◽  
Theoretical Study ◽  
Rotational Quantum Number ◽  
Spectral Lines ◽  
Vibrational Quantum Number ◽  
Energy Characteristics ◽  
Number Increase ◽  
The Relationship

A theoretical study of four gallium monohalides molecules (GaF, GaCl, GaBr and GaI) of ground state 1∑+ by using computer model is presented to study the energy characteristics of vibrational-rotational levels as a function of the vibrational and rotational quantum number , respectively. The calculations has been performed to examine the vibrational-rotational characteristics of some gallium halides molecules. These calculations appeared that all energies (Gv, Ev,J, and Fv,J) increase with increasing vibrational and rotational quantum number and by increasing the vibrational quantum number, and by increasing the vibrational quantum number, the vibrational constant will decrease. Also theoretical study of spectra of these molecules for ground state 1∑+ has been carried out. The values of spectral lines R(J) and P(J) were calculated and the relationship between the spectral lines and the rotational quantum number was established. The results appeared the spectra line values R(J) increases when the values of rotational quantum number decrease but the spectra line values P(J) decrease when the values of rotational quantum number increase, also the spectra line values P(J) decrease when the values of (m) increase, while the values of R(J) increase at first, then decrease showing Fortrar parabola.

New organic luminophores on the basis of cyano- and dicyanopyridines

1986 ◽  
Vol 51 (5) ◽  
pp. 1061-1070 ◽  
Author(s):  
Štefan Marchalín ◽  
Jan Fähnrich ◽  
Milan Popl ◽  
Josef Kuthan
Keyword(s):  
Solvent Effect ◽  
Fluorescence Spectra ◽  
Spectral Characteristics ◽  
Stokes Shift ◽  
Conformational Structure ◽  
Absorption And Fluorescence Spectra ◽  
Organic Luminophores ◽  
The Relationship ◽  
Derivatives Of

Absorption and fluorescence spectra of solutions of cyanopyridine derivatives of polyphenylene type, II-VIII, were investigated. The spectral characteristics determined are interpreted in relation to the probable conformational structure of the investigated substances in the states S0 and S1. The relationship between the Stokes shift and the solvent effect on the fluorescence spectra is discussed.

Binary Dinitrogen Complexes of Rhodium, Rh(N2)n (where n = 1–4), in Low Temperature Matrices

1973 ◽  
Vol 51 (20) ◽  
pp. 3332-3343 ◽  
Author(s):  
Geoffrey A. Ozin ◽  
Anthony Vander Voet
Keyword(s):  
Field Approximation ◽  
Spectral Lines ◽  
Site Symmetry ◽  
Reaction Products ◽  
Solid Nitrogen ◽  
Dinitrogen Complexes ◽  
The Individual ◽  
A Site ◽  
Solid Argon ◽  
The Relationship

The products of the cocondensation reactions of Rh atoms with N2 and N2/Ar mixtures at 10 °K are investigated by matrix isolation infrared spectroscopy and are shown to be binary dinitrogen complexes of the form Rh(N2)n. Examination of the reaction products in pure 14N2, 15N2, 14N2/15N2, and in dilute Ar/14N2, Ar/14N2/15N2, and Ar/14N2/14N15N/15N2 matrices establish the values of n to be 1–4. Isotopic frequencies are computed for the NN stretching modes of the individual dinitrogen complexes on the basis of the Cotton–Kraihanzel (C.K.) force field approximation and are found to be in close agreement with observed values. Trends in the best fit C.K. force constants for Rh(N2)n (n = 1–4) and the thermodynamic stabilities of the individual complexes as indicated by the function ΔHcn, a measure of the enthalpy of decomposition, are discussed. Comparisons are made between Ni(N2)n and Rh(N2)n (where n = 1–4). The structure of Rh(N2)4 in solid nitrogen is shown to be that of a distorted tetrahedron. Calculations show that a site symmetry of D2d for Rh(N2)4 satisfactorily accounts for all of the spectral lines observed for the complex in nitrogen. In solid argon, Rh(N2)4 appears to have an approximately regular tetrahedral structure. The relationship between RhN2 and N2 chemisorbed on Rh metal is discussed and compared with the analogous Ni–, Pd–, and Pt–nitrogen systems.

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