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.

Raman scattering from impurities in semiconductors. I. General result

1978 ◽  
Vol 56 (5) ◽  
pp. 550-559 ◽  
Author(s):  
Robert Barrie ◽  
I. W. Sharpe
Keyword(s):  
Raman Scattering ◽  
General Result ◽  
Adiabatic Approximation ◽  
Phonon Coupling ◽  
Mathematical Technique ◽  
Impurity Site ◽  
Absorption And Emission ◽  
Systematic Fashion ◽  
Impurities In Semiconductors ◽  
Electron Phonon Coupling

A mathematical technique previously used for studying absorption and emission from impurity centres in semiconductors is applied to Raman scattering from such centres. The usual adiabatic approximation is not made. 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. These traces are evaluated for a particular type of electron–phonon coupling.

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.

scholarly journals Stellar magnetic imaging from spectropolarimetric data

1996 ◽  
Vol 176 ◽  
pp. 53-60 ◽  
Author(s):  
J.-F. Donati
Keyword(s):  
Small Amplitude ◽  
High Accuracy ◽  
Spectral Lines ◽  
New Method ◽  
Doppler Imaging ◽  
Magnetic Imaging ◽  
Active Stars ◽  
Surface Fields ◽  
Very High

In this paper, I will review the capabilities of magnetic imaging (also called Zeeman-Doppler imaging) to reconstruct spot distributions of surface fields from sets of rotationnally modulated Zeeman signatures in circularly polarised spectral lines. I will then outline a new method to measure small amplitude magnetic signals (typically 0.1% for cool active stars) with very high accuracy. Finally, I will present and comment new magnetic images reconstructed from data collected in 1993 December at the Anglo-Australian Telescope (AAT).

scholarly journals A New Method of Wavelength Calibration for LAMOST by Combining Short- and Long-Exposure Spectral Lines

2012 ◽  
Vol 29 (1) ◽  
pp. 66-71 ◽  
Author(s):  
G. H. Ye ◽  
J. Zhu ◽  
Z. F. Ye
Keyword(s):  
Spectral Lines ◽  
New Method ◽  
Short Exposure ◽  
Selected Lines ◽  
Wavelength Calibration ◽  
Calibration Methods

AbstractIn wavelength calibration using arc lines, the normal approach is to use the strongest unsaturated lines, leaving weak lines unused. A new method is proposed in this paper, which not only utilizes the strong spectral lines, but also makes most use of weak spectral lines. In order to validate the effectiveness of the method we propose, experiments are performed on simulated spectra. Firstly, two kinds of spectra are generated: one with a short exposure and another with a long exposure. Secondly, calibration lines are chosen from the short exposure and long exposure spectra separately according to some rules. Thirdly, the initial wavelength calibration is completed by using the selected short-exposure lines. Fourthly, the approximate centroids of the selected long-exposure lines are obtained by utilizing the result of the initial wavelength calibration. These are then adjusted iteratively to obtain the centroids. Finally, the selected lines from the short- and long-exposures are combined to obtain the final wavelength calibration. Compared with traditional calibration methods which only use short exposures and strong lines, the proposed method is shown to be more accurate.

PHONON BROADENING OF IMPURITY SPECTRAL LINES: I. GENERAL THEORY

1963 ◽  
Vol 41 (7) ◽  
pp. 1135-1173 ◽  
Author(s):  
Kyoji Nishikawa ◽  
Robert Barrie
Keyword(s):  
General Theory ◽  
Small Perturbation ◽  
Adiabatic Approximation ◽  
Green’S Functions ◽  
Spectral Lines ◽  
Dielectric Susceptibility ◽  
Lattice Vibrations ◽  
Subsequent Calculation ◽  
Double Time ◽  
Bound Electron

The theory of the phonon broadening of impurity spectral lines is discussed within the framework of a Kubo-type formulation of the adiabatic dielectric susceptibility and the subsequent calculation of this using double-time Green's functions. The interaction of the bound electron (or hole) with the lattice vibrations is assumed to be weak and is treated as a small perturbation of the independent systems of electron and vibrating lattice; the use of the adiabatic approximation is thereby avoided. The cases in which the bound carrier states are degenerate and nondegenerate are discussed separately. The results are compared with previous work in the field.

Some important notes on ASTA software: A new method of analysis of simple and complex emission and absorption spectral lines

2019 ◽  
Vol 26 ◽  
pp. 14-34 ◽  
Author(s):  
D. Tzimeas ◽  
D. Stathopoulos ◽  
E. Danezis ◽  
E. Lyratzi ◽  
A. Antoniou
Keyword(s):  
Spectral Lines ◽  
New Method

scholarly journals Measuring precise radial velocities on individual spectral lines

2018 ◽  
Vol 620 ◽  
pp. A47 ◽  
Author(s):  
X. Dumusque
Keyword(s):  
Standard Deviation ◽  
Spectral Line ◽  
Spectral Lines ◽  
New Method ◽  
Statistical Techniques ◽  
Stellar Activity ◽  
New Approach ◽  
Novel Approach ◽  
The One ◽  
Individual Line

Context. Stellar activity is the main limitation to the detection of an Earth-twin using the radial-velocity (RV) technique. Despite many efforts in trying to mitigate the effect of stellar activity using empirical and statistical techniques, it seems that we are facing an obstacle that will be extremely difficult to overcome using current techniques. Aims. In this paper, we investigate a novel approach to derive precise RVs considering the wealth of information present in high-resolution spectra. Methods. This new method consists of building a master spectrum from all available observations and measure the RVs of each individual spectral line in a spectrum relative to this master. When analysing several spectra, the final product of this approach is the RVs of each individual line as a function of time. Results. We demonstrate on three stars intensively observed with HARPS that our new method gives RVs that are extremely similar to the one derived from the HARPS data reduction software. Our new approach to derive RVs demonstrates that the non-stability of daily HARPS wavelength solution induces night-to-night RV offsets with an standard deviation of 0.4 m s−1, and we propose a solution to correct for this systematic. Finally, and this is probably the most astrophysically relevant result of this paper, we demonstrate that some spectral lines are strongly affected by stellar activity while others are not. By measuring the RVs on two carefully selected subsample of spectral lines, we demonstrate that we can boost by a factor of two or mitigate by a factor of 1.6 the red noise induced by stellar activity in the 2010 RV measurements of α Cen B. Conclusions. By measuring the RVs of each spectral line, we are able to reach the same RV precision as other approved techniques. In addition, this new approach allows us to demonstrate that each spectral line is differently affected by stellar activity. Preliminary results show that studying in details the behaviour of each spectral line is probably the key to overcome the obstacle of stellar activity.

New Method for Spectral Line Shape Fitting and Critique on the Voigt Line Shape Model

1995 ◽  
Vol 49 (10) ◽  
pp. 1438-1453 ◽  
Author(s):  
Pekka E. Saarinen ◽  
Jyrki K. Kauppinen ◽  
Jari O. Partanen
Keyword(s):  
Spectral Line ◽  
Line Shape ◽  
Linear Prediction ◽  
Molecular Spectroscopy ◽  
Spectral Lines ◽  
New Method ◽  
Detailed Knowledge ◽  
Spectral Line Shape ◽  
Shape Fitting ◽  
Parametric Line

In this work we introduce a new method for testing spectral line shape models and optimizing the parameters in any parametric model. Given some general parametric line shape and a piece of a spectrum, the method finds the optimal values for the parameters and gives a number which tells how well the spectrum under consideration is explained by that model. The number of spectral lines under analysis may be more than one, and their exact locations need not be known. This characteristic follows from the property that the method does not need the information about line positions and amplitudes at all. Thus, in the absence of a singlet line, a set of overlapping lines can also be analyzed. The analysis is carried out in the signal domain by utilizing linear prediction. Application examples of the method to a molecular spectrum measured in gas phase are given. The results suggest that the Voigt line shape, despite its common use, is not a correct model in molecular spectroscopy. Its limitations become evident when one is trying to enhance the resolution by linear prediction, which requires detailed knowledge of the line shape. Instead a stochastic model, which is also tested, turns out to be rather promising.

The Interpretation of Line Profiles

1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki
Keyword(s):  
Magnetic Fields ◽  
Atomic Physics ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Inhomogeneous Structure ◽  
The Sun ◽  
Line Profiles ◽  
Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

Selective Sampling and Orientation of Non-Homogeneous Tissues

1968 ◽  
Vol 26 ◽  
pp. 98-99
Author(s):  
C. C. Clawson ◽  
L. W. Anderson ◽  
R. A. Good
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Random Sampling ◽  
New Method ◽  
Microscope Examination ◽  
Small Areas ◽  
Selective Sampling ◽  
Large Numbers ◽  
Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

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