scholarly journals Role of Beam Foil Spectroscopy in Understanding Basic Plasma Processes on the Sun

1990 ◽  
Vol 142 ◽  
pp. 439-440
Author(s):  
G. Krishnamurty ◽  
P. Meenakshi Raja Rao ◽  
P. Sarswathy ◽  
B.N. Raja Sekhar
Keyword(s):  
Quantitative Analysis ◽  
Spectral Line ◽  
Transition Probabilities ◽  
Radiative Transition ◽  
Decay Process ◽  
The Sun ◽  
Time Resolved ◽  
Beam Foil

Beam-Foil spectroscopy(BFS) has proved to be a valuable technique for the determination of radiative lifetimes of excited atomic levels leading to the evaluation of the transition probabilities. The time- resolved nature of the decay process in a collisionless environment is a unique characterstic of the beam-foil light source. The relevance of BFS to astrophysics comes from the importance of radiative transition probabilities in the quantitative analysis of optical spectra. Stellar abundances are obtained from the intensity of a spectral line which essentially is a product of the abundance of the element in the source and the probability of the transition. Thus the evaluation of accurate values of transition probabilities contribute significantly to stellar abundance analysis.

scholarly journals Committee 2: Transition Probabilities

1970 ◽  
Vol 14 (1) ◽  
pp. 127-128
Author(s):  
R. H. Garstang
Keyword(s):  
Transition Probabilities ◽  
Conference Report ◽  
Atomic Transition ◽  
National Bureau ◽  
Complete Coverage ◽  
Lifetime Measurements ◽  
Forbidden Transition ◽  
Beam Foil ◽  
Supply Information

A very great deal of work has been done during the last three years on the determination of atomic transition probabilities, and complete coverage here is impossible. Wiese and his staff at the National Bureau of Standards, Washington, have continued to collect all numerical results, and they can supply information as to what is available for any particular atom. They have published (1) a critical compilation of atomic transition probabilities for the atoms sodium to calcium (inclusive) in essentially the same way as an earlier compilation covered hydrogen to neon. At the time of writing a complete new bibliography is also in preparation (2), which will be published as NBS Special Publication 320 and which is complete up to June 1969. Review articles published include that of Layzer and Garstang (3) on theoretical allowed and forbidden transition probabilities, and the two volume conference report (4) covers beam foil spectroscopy (including lifetime measurements) in some detail. A fairly complete review of forbidden line transition probabilities was given by Garstang (5), where references to many original papers may be found. In the following we shall confine ourselves to mentioning a few areas of particular interest; detailed references can be traced through the bibliographies, reviews and abstracting journals.

scholarly journals Quantitative analysis of time-resolved RHEED during growth of vertical nanowires

Nanoscale ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 5471-5482
Author(s):  
Julian Jakob ◽  
Philipp Schroth ◽  
Ludwig Feigl ◽  
Daniel Hauck ◽  
Ullrich Pietsch ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Quantitative Analysis ◽  
Time Resolved

In situ RHEED enables a height-resolved determination of the crystal structure of vertical nanowires via self-shadowing and ensemble shadowing.

The Determination of Zinc Oxide in Rubber Vulcanizates by X-Ray Diffraction

1960 ◽  
Vol 33 (3) ◽  
pp. 890-898
Author(s):  
Stephen H. Laning ◽  
Melvin P. Wagner ◽  
John W. Sellers
Keyword(s):  
Zinc Oxide ◽  
Quantitative Analysis ◽  
Analytical Method ◽  
Direct Determination ◽  
Zinc Stearate ◽  
Photographic Film ◽  
Reaction Products ◽  
X Ray

Abstract Zinc oxide is a necessary component in most accelerator-sulfur vulcanization systems. While it is not an accelerator, its presence leads to increased modulus, i.e., tighter cures. The manner in which it can effect this better cure is not completely clear. Some insight into the role of zinc oxide has been gained through the analysis of the vulcanizate for reaction products of zinc, such as zinc stearate, the zinc salts of the accelerators, and zinc sulfide. However, these products may not account for all of the zinc oxide which has reacted. An analytical method for the direct determination of unreacted zinc oxide in vulcanizates was therefore needed. The determination of zinc oxide in rubber vulcanizates has received scant attention. Wet-chemical techniques for analysis of the sample after ashing provide only the total amount of zinc from which the amount of unreacted zinc oxide cannot be determined. Endter has reported the use of the Debye-Scherrer x-ray technique for the identification of zinc oxide in rubber samples. While similar to the method developed in this laboratory, Endter employed photographic film for recording the diffraction pattern, and special sample preparation was required to accommodate the photographic technique. This method was satisfactory for qualitative identification of zinc oxide, but was difficult to use for quantitative analysis. Subsequent to this investigation Hagino et al. described the use of x-ray diffractometry for the determination of the mixing ratio of ingredients compounded in rubber. This method was also suggested for the quantitative analysis of zinc oxide, but no studies were reported. During a study in this laboratory to determine the role of zinc oxide in the vulcanization of rubber, a new analytical method, based on x-ray diffractometry, was developed. The method was rapid, nondestructive, and simple. The data were reliable and accurate.

scholarly journals First-principles interpretation of electron transport though single-molecule junctions using molecular dynamics of electron attached states

2021 ◽  
Author(s):  
Dávid P. Jelenfi ◽  
Attila Tajti ◽  
Péter G. Szalay
Keyword(s):  
Molecular Dynamics ◽  
Electron Transport ◽  
Single Molecule ◽  
Transition Probabilities ◽  
Normal Mode Analysis ◽  
Mode Analysis ◽  
Bending Vibrations ◽  
Time Resolved ◽  
State Models

The electron transport through the single-molecule junction of 1,4-Diaminobenzene (BDA) is modeled using ab initio quantum-classical molecular dynamics of electron attached states. Observations on the nature of the process are made by time-resolved analysis of energy differences, non-adiabatic transition probabilities and the spatial distribution of the excess electron. The role of molecular vibrations that facilitate the transport by being responsible for the periodic behaviour of these quantities is shown using normal mode analysis. The results support a mechanism involving the electron's direct hopping between the electrodes, without its presence on the molecule, with the prime importance of the bending vibrations that periodically alter the molecule{electrode interactions. No relevant differences are found between results provided by the ADC(2) and SOS-ADC(2) excited state models. Our approach provides an alternative insight into the role of nuclear motions in the electron transport process, one which is more expressive from the chemical perspective.

Determination of absolute atomic transition probabilities using time resolved optical pumping

1977 ◽  
Vol 21 (1) ◽  
pp. 116-120 ◽  
Author(s):  
L.R. Carlson ◽  
S.A. Johnson ◽  
E.F. Worden ◽  
C.A. May ◽  
R.W. Solarz ◽  
...  
Keyword(s):  
Optical Pumping ◽  
Transition Probabilities ◽  
Atomic Transition ◽  
Time Resolved

scholarly journals Definition and Practical Realization of the Reference Frame in the FK5 - The Role of Planetary Dynamics and Stellar Kinematics in the Definition

1980 ◽  
Vol 56 ◽  
pp. 331-340 ◽  
Author(s):  
Walter Fricke
Keyword(s):  
Reference Frame ◽  
Reference System ◽  
The Sun ◽  
Practical Realization ◽  
Stellar Kinematics ◽  
Planetary Dynamics ◽  
Astronomical Constants ◽  
Fundamental Reference

AbstractThe formulation of the fundamental reference system to be represented by the FK5 includes the determination of the equinox and equator on the basis of planetary dynamics and the application of the new expressions for the general precession in longitude adopted in the IAU (1976) System of Astronomical Constants. The role of hypotheses which entered the determination of the lunisolar precession is explained. Results are presented for the equinox and equator of the FK5 which are based on observations of the Sun, planets, and lunar occultations.

Role of Beam Foil Spectroscopy in Understanding Basic Plasma Processes on the Sun

1990 ◽  
pp. 439-440
Author(s):  
G. Krishnamurty ◽  
P. Meenakshi Raja Rao ◽  
P. Sarswathy ◽  
B. N. Raja Sekhar
Keyword(s):  
The Sun ◽  
Beam Foil

Laboratory measurements of oscillator strengths and their astrophysical applications1This review is part of a Special Issue on the 10th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas.

2011 ◽  
Vol 89 (4) ◽  
pp. 387-393 ◽  
Author(s):  
J.C. Pickering ◽  
R. Blackwell-Whitehead ◽  
A.P. Thorne ◽  
M. Ruffoni ◽  
C.E. Holmes
Keyword(s):  
Transition Probabilities ◽  
Oscillator Strengths ◽  
Astronomical Instrumentation ◽  
Time Resolved ◽  
International Colloquium ◽  
Fourier Transform Spectrometry ◽  
Laboratory Plasmas ◽  
Astrophysical Objects ◽  
Improved Accuracy

We present an overview of current needs for accurate laboratory atomic transition probabilities (log(gf)) for astrophysical applications, particularly for iron group element spectra in the IR, optical, UV, and VUV spectral regions. Examples are given of our recent measurements, undertaken using the combination of high-resolution Fourier transform spectrometry and time-resolved laser-induced fluorescence. Laboratory measured log(gf) values are particularly important for the determination of elemental abundances in astrophysical objects. Advances in astronomical instrumentation, particularly access to underexplored regions (IR, vacuum UV,VUV), require improved accuracy and completeness of the atomic database for meaningful analyses of astrophysical spectra.

scholarly journals The Position of the Sun in the HR Diagram

1978 ◽  
Vol 80 ◽  
pp. 89-90
Author(s):  
Don C. Barry
Keyword(s):  
Quantitative Analysis ◽  
Spectral Line ◽  
Spectral Type ◽  
Main Sequence ◽  
Solar Spectrum ◽  
Absolute Magnitude ◽  
Systematic Difference ◽  
The Sun ◽  
The Absolute ◽  
Hr Diagram

Since the absolute magnitude of the Sun is known accurately and the solar spectrumdefinesspectral type G2 V, it would appear that the position of the Sun in the HR diagram is well established. However, the color of the Sun and its metallicity relative to other stars remains controversial. It is known from theory that stellar groups of differing composition will have different main sequences.The observed difference in the strength of the metallic lines in Coma stars relative to Hyades stars is caused by a systematic difference in [Fe/H] of less than 0.2 dex or 50%. Photographs and quantitative measures of the systematic differences between the Hyades and Coma spectra are presented. Visual comparison and quantitative analysis of the solar spectrum relative to Hyades and Coma spectra reveal that the Sun is metal rich similar to the Hyades stars rather than of normal disk metallicity as represented by Coma stars. Evidence is presented showing that the color and spectral line strengths of the Sun are more similar to stars classified G3 and G4 in the literature than G2. If the Hyades modulus is y = 3m.25, the (B-V) color of the Sun must be 0m.65 or redder for the Sun to be on or above the Hyades main sequence.

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