scholarly journals Computation of the Absorption Coefficient for Diatomic Molecules

1994 ◽  
Vol 146 ◽  
pp. 271-281
Author(s):  
Mats Larsson
Keyword(s):  
Absorption Coefficient ◽  
Electronic States ◽  
Molecular Data ◽  
Stellar Atmosphere ◽  
Stellar Atmospheres ◽  
Electronic Transitions ◽  
Molecular Electronic ◽  
Molecular Physics ◽  
Cool Star ◽  
Molecular Lines

Molecules in stellar atmospheres play key roles, not only as promoters of our understanding of stars, but also as actors affecting the structures of the atmospheres. In particular cool star atmospheres are affected by molecular opacities, and during recent years it has become clear that also weak molecular lines are of crucial structural importance. Extensive molecular data are thus needed in order to correctly model the structure of a stellar atmosphere and the transport of radiation through it. The basis for how such molecular data are acquired constitutes the theme of the present article. As will follow below, results from different subfields of molecular physics are needed in order to obtain a complete picture of the absorption of radiation by molecules. This article will only consider allowed molecular electronic transitions, i.e. dipole transitions betweendifferentelectronic states; however, the presentation and the formulae may easily be modified to be valid for transitions between levels within a single electronic state.

scholarly journals Presentation and Interpretation of High Resolution Infrared Spectra of Late-Type Stars

1974 ◽  
Vol 3 ◽  
pp. 255-268 ◽  
Author(s):  
R. I. Thompson
Keyword(s):  
Stellar Evolution ◽  
Carbon Star ◽  
Stellar Atmosphere ◽  
Stellar Atmospheres ◽  
Stellar Spectra ◽  
Cool Star ◽  
Convective Mixing ◽  
Processed Material ◽  
Carbon Compounds ◽  
Red Giant

Current interest in stellar evolution is concentrated on the life of a star after it has left the main sequence. Of particular interest are the red giant or supergiant periods during the hydrogen and helium shell burning phases. Convective mixing during these stages can mix nuclear processed material to the surface where it may be viewed by spectroscopic methods. It is imperative that this rare chance to view processed material be exploited fully to increase our knowledge of stellar evolution.The observation and interpretation of cool star spectra has its own particular set of problems and advantages. A particular difficulty is the formation of molecules at the low temperatures which occur in the atmospheres of late stars. Not only must the particularly complex spectra of molecules be dealt with but the problem of chemical equilibrium in the atmosphere must be solved accurately before quantitative analysis may be performed. The formation of molecules, however, has one advantage in that it very dramatically separates those stars with carbon to oxygen ratios greater than one from those with ratios less than one. It is the very high dissociation energy of 11.1 eV for the CO molecule which performs this separation. If carbon is less abundant than oxygen all of the carbon is tied up in CO and only oxides are formed in the stellar atmosphere which produce typical M star spectra. If, however, carbon is more abundant than oxygen then carbon compounds such as C2 are formed in place of the oxides and a carbon star spectrum is formed. One of the great advantages of infrared stellar spectra is that it is the only ground based technique for observing CO in stellar atmospheres.

scholarly journals Atomic and Molecular Data for Observations of the Interstellar Medium With the Hubble Space Telescope

1992 ◽  
Vol 9 ◽  
pp. 559-560
Author(s):  
Donald C. Morton
Keyword(s):  
High Resolution ◽  
Hubble Space Telescope ◽  
Laboratory Data ◽  
Molecular Data ◽  
Electronic Transitions ◽  
High Signal ◽  
Line Profiles ◽  
Molecular Electronic ◽  
Signal To Noise ◽  
Ground Term

The Goddard High Resolution Spectrograph (GHRS) on the HST, with resolving powers up to 94000 or 3.2 km s−1, is giving us a new look at interstellar absorption lines in the range 1090 to 3350 Å (Savage et al 1991, Cardelli et al 1991, Smith et al 1991). The high signal-to-noise ratios possible with the digicon detectors provide precise line profiles suitable for studying individual velocity components. Morton (1991) has summarized the relevant laboratory data on wavelengths and f-values for the atomic absorptions from the ground term likely to be detected by the HST, and Hsu and Hayden Smith (1977) have provided a useful list of candidate molecular electronic transitions.

scholarly journals Independent Sources of Information-Theoretic Descriptors of Electronic States

2020 ◽  
pp. 106-115
Author(s):  
Roman F. Nalewajski
Keyword(s):  
Information Sources ◽  
Electronic States ◽  
The State ◽  
Sources Of Information ◽  
Molecular Electronic ◽  
Information Theoretic ◽  
State Entropy ◽  
Phase Current ◽  
Electronic Wavefunctions ◽  
Information Order

The need for resultant measures of the Information-Theoretic (IT) content of molecular electronic wavefunctions, combining the information contributions due to the probability and phase/current distributions, is reemphasized. Complementary measures of the state entropy (disorder) and information (order) contents are reexamined, the continuities of wavefunction components are summarized, and the probability acceleration concept is used to determine the current and information sources. The experimental elimination of the state uncertainties is discussed and limitations in this information-acquirement process imposed by the Heisenberg indeterminacy principle are commented upon.

Dynamic Fields and Response Properties

2020 ◽  
pp. 473-554
Author(s):  
Jochen Autschbach
Keyword(s):  
Absorption Coefficient ◽  
Linear Response ◽  
Optical Rotation ◽  
Polarized Light ◽  
Linear Response Theory ◽  
Time Dependent ◽  
Electronic Transitions ◽  
Orbital Theory ◽  
Response Properties ◽  
Set Up

It is shown how electronic transitions can be induced by the interaction with an electromagnetic wave of a suitable frequency. The rate of a transition between two electronic states induced by a time-dependent field is derived. The transition rate expression is used to calculate the absorption coefficient due to electronic transitions. The differential absorption coefficient for left and right circular polarized light is specific to chiral molecules and has different signs for a pair of enantiomers. The discussion then shifts to general functions describing the response of an atom or molecule to an external. The ideas developed thus far are then applied to the dynamic polarizability, molecular linear response functions in general, and the optical rotation. Linear response theory is set up within time-dependent molecular orbital theory. The Chapter concludes with a discussion of non-linear response properties and two-photon absorption.

Atomic and Molecular Electronic States

2012 ◽  
pp. 1-25
Author(s):  
Wai-Kee Li ◽  
Yu-San Cheung ◽  
Kendrew Kin Wah Mak ◽  
Thomas Chung Wai Mak
Keyword(s):  
Electronic States ◽  
Molecular Electronic

scholarly journals ExoMol line list – XXXIV. A rovibrational line list for phosphinidene (PH) in its $X\, {}^3\Sigma ^-$ and $a\, {}^1\Delta$ electronic states

2019 ◽  
Vol 488 (2) ◽  
pp. 2332-2342 ◽  
Author(s):  
Jonathan Langleben ◽  
Jonathan Tennyson ◽  
Sergei N Yurchenko ◽  
Peter Bernath
Keyword(s):  
Ab Initio ◽  
Electronic States ◽  
Stellar Atmospheres ◽  
Spin Splitting ◽  
Mean Square ◽  
Data Bases ◽  
Line List ◽  
Line Intensities ◽  
Experimental Transition ◽  
Correction Terms

ABSTRACT A rovibronic line list for the ground (X 3Σ−) and first excited (a 1Δ) states of phosphinidene, 31PH, is computed. The line list is designed for studies of exoplanetary and cool stellar atmospheres with temperatures up to 4000 K. A combination of empirical and ab initio data is used to produce the line list: potential energy curves (PECs) are fitted using experimental transition frequencies; these transitions are reproduced with a root mean square error of 0.01 cm−1. The nuclear Schrödinger equation is solved using these PECs plus Born–Oppenheimer and spin splitting correction terms. Line intensities and Einstein   A coefficients are computed using ab initio dipole moment curves for X–X and a–a transitions. The resulting LaTY line list, which contains 65 055 transitions for 2528 rovibronic states up to 24 500 cm −1 and J = 80, is used to simulate spectra in emission and absorption for a range of temperatures. The line list is made available in electronic form at the CDS and ExoMol data bases.

Bonding and electronic states of boron in silicon nanowires characterized by an infrared synchrotron radiation beam

Nanoscale ◽  
2015 ◽  
Vol 7 (16) ◽  
pp. 7246-7251 ◽  
Author(s):  
N. Fukata ◽  
W. Jevasuwan ◽  
Y. Ikemoto ◽  
T. Moriwaki
Keyword(s):  
Synchrotron Radiation ◽  
Excited States ◽  
Silicon Nanowires ◽  
Ground State ◽  
Electronic States ◽  
Electronic Transitions ◽  
Synchrotron Radiation Beam ◽  
Radiation Beam ◽  
Acceptor Atom ◽  
Ft Ir

The first report of B local vibrational peaks and electronic transitions of a bound hole from the ground state of a B acceptor atom to excited states by means of micro-FT-IR measurements using an IR-SR beam.

Accurate Reconstruction of the Density of States in a-Si:H by Photothermal and Photoconductive Spectra.

1993 ◽  
Vol 297 ◽  
Author(s):  
G. Amato ◽  
F. Giorgis ◽  
C. Manfredotti
Keyword(s):  
Iterative Method ◽  
Absorption Coefficient ◽  
Fermi Level ◽  
Density Of States ◽  
Localized States ◽  
Electronic Transitions ◽  
Photothermal Deflection Spectroscopy ◽  
Derivative Method ◽  
Photothermal Deflection ◽  
Made In

The distribution of occupied states in a-Si:H has been inferred by applying a new self- consisting iterative method to the absorption coefficient spectra. This procedure does not require any assumption about the localized states below the Fermi level, and provides a more accurate insight with respect to the simple derivative method. Numerical simulations have been made in order to probe the reliability of our method. The optical spectra have been obtained by means of Photothermal Deflection Spectroscopy (PDS) and Constant Photocurrent Method (CPM); the comparison between the results as obtained by the two techniques suggests that different sensitivities to electronic transitions are involved; this can be used to infer information about the unoccupied defects.

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