scholarly journals The Ionisation Equilibrium for Heavy Elements

1968 ◽  
Vol 34 ◽  
pp. 205-208
Author(s):  
D.R. Flower
Keyword(s):  
Radiation Field ◽  
Optical Depth ◽  
Cross Sections ◽  
Ground State ◽  
Spectral Region ◽  
Heavy Elements ◽  
First Approximation ◽  
Initial Work ◽  
Far Ultraviolet ◽  
Better Than

Calculations are being made of the distribution of the ions of heavy elements in planetary nebulae. Initial work has been concentrated on the central or He2+ zone of planetaries. The optical depths of ions of C, N, O, and Ne have been computed using ground state ionisation cross-sections and using approximations which should be substantially better than hydrogenic. A comparison has been made between the combined optical depth of the heavy elements and the optical depth of He+ in the far ultraviolet. The optical depths of the heavy elements in this spectral region may become significant, but a reasonable first approximation to the radiation field may be obtained by neglecting the absorption of all ions except He+. The distribution of the ions of the heavy elements has been calculated on this assumption.

scholarly journals The FUSE Mission: Atomic Data Needs in the 900–1200 Å Spectral Region

2002 ◽  
Vol 12 ◽  
pp. 79-81
Author(s):  
Kenneth R. Sembach
Keyword(s):  
High Resolution ◽  
Solar System ◽  
Interstellar Medium ◽  
Absorption Line ◽  
Ground State ◽  
Spectral Region ◽  
Theoretical Calculations ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Far Ultraviolet

AbstractThe Far Ultraviolet Spectroscopic Explorer (FUSE) is presently producing high resolution (R ∼ 20,000) absorption-line spectra of astronomical objects ranging from Solar System planets to quasars. The 900-1200 Å spectral region observed by FUSE is exceedingly rich in atomic and molecular transitions arising out of the ground state. It is already clear from early FUSE observations that the atomic data (e.g., oscillator strengths) for some transitions are considerably different than those predicted by theoretical calculations. I briefly describe the most pressing oscillator strength needs in this wavelength range for studies of the interstellar medium.

COMMENT ON A FREQUENT ERROR IN CALCULATIONS OF THE Γn/Γf RATIO

2009 ◽  
Vol 18 (04) ◽  
pp. 823-829 ◽  
Author(s):  
K. SIWEK-WILCZYŃSKA ◽  
J. WILCZYŃSKI
Keyword(s):  
Binding Energy ◽  
Cross Sections ◽  
Ground State ◽  
Residual Nucleus ◽  
Heavy Elements ◽  
Shell Effect ◽  
Excitation Energies ◽  
Neutron Binding Energy ◽  
Energy Dependent ◽  
Leading Journals

In the last decade some 20–30 publications in leading journals appeared in which cross sections for production of super-heavy elements are calculated with an erroneous formula for the Γn/Γf ratio. The erroneous treatment of shell structure corrections leads to an energy-dependent fission barrier that is inserted to the expression for the fission width Γf. In this approach the shell effect in the residual nucleus that emitted the neutron is ignored. We give examples of calculations that illustrate the deviations of the erroneous formula from the correct one. The errors reach several orders of magnitude, especially for low excitation energies and those compound nuclei for which large ground-state shell effect exceeds the neutron binding energy.

scholarly journals High spectral resolution ozone absorption cross-sections – Part 1: Measurements, data analysis and comparison with previous measurements around 293 K

2014 ◽  
Vol 7 (2) ◽  
pp. 609-624 ◽  
Author(s):  
V. Gorshelev ◽  
A. Serdyuchenko ◽  
M. Weber ◽  
W. Chehade ◽  
J. P. Burrows
Keyword(s):  
Data Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Spectral Resolution ◽  
Spectral Region ◽  
Uncertainty Budget ◽  
High Spectral Resolution ◽  
Absorption Cross ◽  
Ozone Absorption ◽  
Better Than

Abstract. In this paper we discuss the methodology of taking broadband relative and absolute measurements of ozone cross-sections including uncertainty budget, experimental set-ups, and methods for data analysis. We report on new ozone absorption cross-section measurements in the solar spectral region using a combination of Fourier transform and echelle spectrometers. The new cross-sections cover the spectral range 213–1100 nm at a spectral resolution of 0.02–0.06 nm in the UV–visible and 0.12–0.24 nm in the IR at eleven temperatures from 193 to 293 K in steps of 10 K. The absolute accuracy is better than three percent for most parts of the spectral region and wavelength calibration accuracy is better than 0.005 nm. The new room temperature cross-section data are compared in detail with previously available literature data. The temperature dependence of our cross-sections is described in a companion paper (Serdyuchenko et al., 2014).

scholarly journals High spectral resolution ozone absorption cross-sections – Part 1: Measurements, data analysis and comparison with previous measurements around 293 K

2013 ◽  
Vol 6 (4) ◽  
pp. 6567-6611 ◽  
Author(s):  
V. Gorshelev ◽  
A. Serdyuchenko ◽  
M. Weber ◽  
W. Chehade ◽  
J. P. Burrows
Keyword(s):  
Data Analysis ◽  
Cross Sections ◽  
Spectral Resolution ◽  
Spectral Region ◽  
Uncertainty Budget ◽  
Companion Paper ◽  
High Spectral Resolution ◽  
Absorption Cross ◽  
Ozone Absorption ◽  
Better Than

Abstract. In this paper we discuss the methodology of taking broadband relative and absolute measurements of ozone cross-sections including uncertainty budget, experimental set-ups, and methods for data analysis. We report on new ozone absorption cross-section measurements in the solar spectral region using a combination of Fourier transform and echelle spectrometers. The new cross-sections cover the spectral range 213–1100 nm at a spectral resolution of 0.02–0.06 nm in the UV-vis and 0.12–0.24 nm in the IR at eleven temperatures from 193 to 293 K in steps of 10 K. The absolute accuracy is better than three percent for most parts of the spectral region and wavelength calibration accuracy is better than 0.005 nm. The new room temperature cross-sections data are compared in detail with previously available literature data. The temperature dependence of our cross-sections is described in a companion paper.

CALCULATIONS OF THE FORMATION CROSS SECTIONS FOR SYNTHESIS OF Z = 114–118 NUCLEI IN 48Ca INDUCED REACTIONS

2009 ◽  
Vol 18 (04) ◽  
pp. 1079-1083 ◽  
Author(s):  
K. SIWEK-WILCZYŃSKA ◽  
A. BOROWIEC ◽  
J. WILCZYŃSKI
Keyword(s):  
Saddle Point ◽  
Cross Sections ◽  
Ground State ◽  
Evaporation Residue ◽  
Heavy Elements ◽  
Experimental Cross ◽  
Fission Barriers ◽  
The Cross

Calculations of the evaporation-residue cross sections for production of super-heavy elements of Z = 114–118 in hot fusion (3n and 4n) reactions induced by 48 Ca projectiles on Pu , Am , Cm and Cf targets are presented. Results of calculations are compared with the cross sections measured by Oganessian et al. in the experiments in which the Z = 114–118 elements had been discovered. Calculations were done for the ground-state masses and fission saddle-point energies of Myers and Swiatecki and Sobiczewski et al. Considerable differences in the theoretical masses result in large differences (of several orders of magnitude) in the predicted cross sections. The ground-state masses and fission barriers of Sobiczewski et al. seem to well reproduce the experimental cross sections.

SPALLATION YIELDS FROM HIGH ENERGY PROTON BOMBARDMENT OF HEAVY ELEMENTS

1957 ◽  
Vol 35 (1) ◽  
pp. 21-37 ◽  
Author(s):  
J. D. Jackson
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Heavy Elements ◽  
Collective Effects ◽  
Comparison With Experiment ◽  
Energy Proton ◽  
Stringent Test ◽  
Neutron Evaporation ◽  
Nuclear Processes ◽  
Mev Protons

The Monte Carlo calculations of McManus and Sharp (unpublished) for the prompt nuclear processes occurring upon bombardment of heavy elements by 400 Mev. protons are combined with a description of the subsequent neutron evaporation to determine spallation cross sections for comparison with experiment. The model employed is a schematic one which suppresses the detailed characteristics of individual nuclei, but gives the over-all behavior to be expected. Many-particle and collective effects such as alpha particle emission and fission are ignored. The computed cross sections are presented in a variety of different graphical forms which illustrate quantitatively the qualitative picture of high energy reactions first given by Serber (1947). The calculations are in general agreement with existing data when fission is not an important effect, but the agreement does not imply a very stringent test of the various features of the model.

Photoablösung von Elektronen bei einigen stabilen negativen Ionen

1970 ◽  
Vol 25 (5) ◽  
pp. 621-626 ◽  
Author(s):  
D. Feldmann
Keyword(s):  
Cross Sections ◽  
Negative Ions ◽  
Better Than

Photodetaehment of electrons from some stable negative ions has been measured. Cross sections of about 10-17 cm2, and the following minimal detachment energies were found: H-: 0.776 eV, C-*: < 0.5 eV, CH-: 0.74 eV, C2- : 3.54 eV, C2H- : 3.73 eV, SO-: 1.09 eV, and SO-: 1.0 eV with an accuracy better than + 0.05 eV.

scholarly journals On the Appearance of a Cooper Minimum in the Photoionization Cross Sections of the Plasma-Embedded Li Atom

2009 ◽  
Vol 2009 ◽  
pp. 1-5 ◽  
Author(s):  
Satyabrata Sahoo ◽  
Y. K. Ho
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Debye Screening Length ◽  
Debye Screening ◽  
Screening Length ◽  
Screening Effect ◽  
Plasma Environment ◽  
Plasma Screening ◽  
Debye Plasma

The plasma screening effect is found to uncover a Cooper minimum in the photoionization cross sections from the ground state of the Li atom embedded in Debye plasma environment. The variation of the location of this minimum with Debye screening length is discussed and analyzed in terms of the instability of the ground state.

Dipole oscillator strength distributions and properties for SO2, CS2, and OCS

1985 ◽  
Vol 63 (3) ◽  
pp. 417-427 ◽  
Author(s):  
Ashok Kumar ◽  
William J. Meath
Keyword(s):  
Oscillator Strength ◽  
Cross Sections ◽  
Ground State ◽  
Strength Properties ◽  
Oscillator Strengths ◽  
Sum Rule ◽  
Strength Data ◽  
Dilute Gases ◽  
Dipole Oscillator ◽  
Strength Distributions

Dipole oscillator strength distributions have been constructed and used to evaluate integrated oscillator strengths, and a variety of dipole oscillator strength properties, for ground state SO2, CS2, and OCS. Each distribution has been constructed by using experimental and theoretical photoabsorption cross sections and by subjecting the resulting dipole oscillator strength data to constraints provided by the Thomas–Reiche–Kuhn sum rule and molar refractivity data for the relevant dilute gases. The discussion includes graphical presentations of how various spectral regions of the dipole oscillator strength distributions contribute to the more important dipole properties.

A SCHEMATIC MODEL FOR (p, xn) CROSS SECTIONS IN HEAVY ELEMENTS

1956 ◽  
Vol 34 (8) ◽  
pp. 767-779 ◽  
Author(s):  
J. D. Jackson
Keyword(s):  
Cross Sections ◽  
Reaction Cross ◽  
Heavy Elements ◽  
Total Reaction Cross Section ◽  
Schematic Model ◽  
Nuclear Temperature ◽  
A Minor ◽  
Neutron Evaporation ◽  
Average Neutron ◽  
Evaporation Stage

A schematic model for the description of (p, xn) reactions in heavy elements is presented. Reactions are divided into two steps, a prompt multiple collision process, followed by an evaporation stage. The various prompt processes are given by the results of Monte Carlo calculations, while the evaporation processes are described by a simplified model assuming constant nuclear temperatures and only neutron evaporation. The resulting (p, xn), and to a minor degree (p, pxn), cross sections are compared with the experimental data of Bell and Skarsgard (1956) in the energy range up to 100 Mev. With an average neutron binding energy of around 7.3 Mev., a nuclear temperature of about 1.8 Mev., and a nuclear radius of 8.0 × 10−13 cm., a reasonable over-all fit can be made to the data for Pb206, Pb207, Pb208, and Bi209. Characteristic fluctuations in the experimental results for the (p, 2n), (p, 3n), and (p, 4n) reactions for all targets seem to be attributable to variations in the total reaction cross section, and are not reproduced by the present model.

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