Semi-empirical electron impact cross sections for atmospheric gases

1969 ◽  
Vol 47 (10) ◽  
pp. 1774-1777 ◽  
Author(s):  
L. R. Peterson ◽  
S. S. Prasad ◽  
A. E. S. Green
Keyword(s):  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Reference List ◽  
Atmospheric Gases ◽  
University Of Florida ◽  
Practical Applications ◽  
Functional Forms ◽  
The University ◽  
Semi Empirical

The present paper summarizes conveniently the electron-impact cross sections for N2, O2, and O used in recent aurora and dayglow studies at the University of Florida. The cross section parameters in their present form are a natural outgrowth of (a) the availability of an increasing number of cross section measurements in the laboratory as well as field observations of spectral intensities, and (b) more realistic calculations.The values presented should serve as a useful interim reference list pending the full analyses of current extensive data. Their usefulness for practical applications to problems in aeronomy is enhanced by their integrable functional forms.

scholarly journals Temperature-Dependent Stimulated Emission Cross-Section in Nd3+:YLF Crystal

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 431
Author(s):  
Giorgio Turri ◽  
Scott Webster ◽  
Michael Bass ◽  
Alessandra Toncelli
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Room Temperature ◽  
Radiative Decay ◽  
Emission Cross Section ◽  
Spectroscopic Properties ◽  
Stimulated Emission ◽  
Different Temperatures ◽  
Stimulated Emission Cross Section ◽  
Semi Empirical

Spectroscopic properties of neodymium-doped yttrium lithium fluoride were measured at different temperatures from 35 K to 350 K in specimens with 1 at% Nd3+ concentration. The absorption spectrum was measured at room temperature from 400 to 900 nm. The decay dynamics of the 4F3/2 multiplet was investigated by measuring the fluorescence lifetime as a function of the sample temperature, and the radiative decay time was derived by extrapolation to 0 K. The stimulated-emission cross-sections of the transitions from the 4F3/2 to the 4I9/2, 4I11/2, and 4I13/2 levels were obtained from the fluorescence spectrum measured at different temperatures, using the Aull–Jenssen technique. The results show consistency with most results previously published at room temperature, extending them over a broader range of temperatures. A semi-empirical formula for the magnitude of the stimulated-emission cross-section as a function of temperature in the 250 K to 350 K temperature range, is presented for the most intense transitions to the 4I11/2 and 4I13/2 levels.

Relative Variation of K- And L-Shell Ionization Cross Sections by Electron Impact

1999 ◽  
Vol 5 (S2) ◽  
pp. 584-585
Author(s):  
X. Llovet ◽  
C. Merlet ◽  
J.M. Fernández-Varea ◽  
F. Salvat
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Carbon Films ◽  
X Rays ◽  
Empirical Formulas ◽  
Relative Variation ◽  
Ionization Cross ◽  
Ionization Cross Sections ◽  
Semi Empirical ◽  
Shell Ionization

Knowledge of inner-shell ionization cross sections by electron impact is needed for quantitative procedures in electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) The common practice is to use semi-empirical formulas, based on the asymptotic limit of the Bethe theory, which sometimes are used beyond their domain of validity. Experimental measurements of ionization cross sections are scarce and affected by considerable uncertainties, thus a mere comparison with experimental data does not permit to draw a definite conclusion abou the accuracy of the various formulas. In this communication, we present new measurements o the relative variation of K- and L-shell ionization cross sections deduced from the counting rate of characteristic x-rays emitted by extremely thin films of Cr, Ni, Cu, Te, Au and Bi bombardec by keV electrons.The studied films were produced by thermal evaporation on backing self-supported 30 nm carbon films.

Absolute cross sections for D2 Lyman and Werner band excitation by controlled electron impact

1984 ◽  
Vol 62 (1) ◽  
pp. 1-9 ◽  
Author(s):  
K. Becker ◽  
J. W. McConkey
Keyword(s):  
Energy Range ◽  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Impact Energy ◽  
Emission Cross Section ◽  
Direct Excitation ◽  
The Cross ◽  
Impact Energies

We have studied the Lyman [Formula: see text] and Werner [Formula: see text] band emissions produced by 20–500-eV electrons incident on molecular deuterium, D2. Emission cross sections of (3.7 ± 0.9) × 10−17 cm2 for the B → X and (3.54 ± 0.74) × 10−17 cm2 for the C → X system have been determined at 100-eV impact energy. Cascading did not play an important role in the [Formula: see text] emission, but it was shown to affect the [Formula: see text] emission seriously, particularly for impact energies below 50 eV. We estimate the cross section for direct excitation of the [Formula: see text] state and the cascade cross section to be 2.95 × 10−17 and 0.75 × 10−17 cm2, at 100 eV respectively. The cascade cross section is 20 ± 10% of the total B → X emission cross section, and is essentially constant in the energy range 300–50 eV, but increases significantly for lower impact energies, e.g., to 40 ± 15% at 27.5 eV. The cross section for the atomic 2p → 1s Lyman α emission from D2 has also been measured and the value of 1.00 × 10−17 cm2 at 100 eV is 20% smaller than the cross section for Lyman α emission from H2.

Excitation of singly-ionized barium ions by electron impact

1970 ◽  
Vol 48 (3) ◽  
pp. 275-278 ◽  
Author(s):  
J. Davis ◽  
S. Morin
Keyword(s):  
Energy Range ◽  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Experimental Measurements ◽  
Barium Ions ◽  
Semiclassical Method ◽  
The Cross

We present cross-section calculations for excitation of singly-ionized barium ions by electron impact over the energy range from 3 to 100 eV. The cross sections were evaluated using Burgess' semiclassical method. Finally, our predictions are compared with two other current techniques and some recent experimental measurements. The agreement was found to be good.

Cross Section Ratios for the Electron Impact Production of Singly and Multiply Ionized Rare Gas Ions

1978 ◽  
Vol 33 (9) ◽  
pp. 1111-1113 ◽  
Author(s):  
F. Egger ◽  
T. D. Mark
Keyword(s):  
Electron Impact ◽  
Cross Section ◽  
Mass Spectrometer ◽  
Cross Sections ◽  
Impact Ionization ◽  
Rare Gas ◽  
Ionization Cross ◽  
Single Ionization ◽  
Multiple Ionization ◽  
Ionization Cross Sections

Electron impact ionization of He, Ne, Ar, Kr and Xe has been studied with a double focussing mass spectrometer Varian MAT CH5. Ratios of various multiple ionization cross sections with respect to single ionization cross sections for He, Ne, Ar, Kr and Xe at electron energies of 50, 100 and 150eV are given. These cross section ratios are com­pared with previous determinations.

The 1 s -2 s excitation of hydrogen atoms by electron impact

1960 ◽  
Vol 258 (1293) ◽  
pp. 245-250 ◽  
Keyword(s):  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Hydrogen Atoms ◽  
Third Order ◽  
The Third ◽  
Intermediate States

The expression for the cross-section obtained from the second Born approximation by including only terms to the third order in the interaction energy is employed to calculate cross-sections for the electron impact excitation of the 2 s level of atomic hydrogen, allow­ance being made for distortion and polarization due to the 1 s , 2 s and 2 p 0.± 1 intermediate states. These cross-sections are compared with the available experimental data.

Measurement of absolute electron-impact excitation cross sections in Ar and N2 using H and H2 emissions as secondary standards

1988 ◽  
Vol 66 (4) ◽  
pp. 349-357 ◽  
Author(s):  
J. L. Forand ◽  
S. Wang ◽  
J. M. Woolsey ◽  
J. W. McConkey
Keyword(s):  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Emission Cross Section ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Dissociative Excitation ◽  
Excitation Cross Sections ◽  
Line Following ◽  
Good Agreement

A detailed description is given of a technique in which emissions from H and H2 are used to calibrate an apparatus used for electron-impact emission cross-section measurements in the wavelength range 90–130 nm. Absolute emission cross sections have been measured at 200 eV electron-impact energy for the 120 nm N I line following dissociative excitation of N2 and for the Ar and Ar+ lines at 104.8, 106.7, 92.0, and 93.8 nm respectively. Good agreement with earlier works is obtained in the case of the N I line when earlier data are renormalized to take into account the recent revision of the cross section for production of Lyman α from H2. Measurements of the 104.8 and 106.7 nm lines suggest a 40% cascade component for the latter line at energies of 200 eV and above.

scholarly journals Momentum Transfer Cross Section for Electrons in Mercury Vapour Derived from Drift Velocity Measurements in Mercury Vapour?Gas Mixtures

1991 ◽  
Vol 44 (6) ◽  
pp. 647 ◽  
Author(s):  
JP England ◽  
MT Elford
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Personal Communication ◽  
Mercury Vapour ◽  
Semi Empirical ◽  
Time Of Flight Method ◽  
Momentum Transfer Cross Section ◽  
Good Agreement

The Bradbury-Nielsen time-of-flight method has been used to measure electron drift velocities at 573 K in pure mercury vapour, a mixture of 46�80% helium-53� 20% mercury vapour and a mixture of 9�37% nitrogen-90� 63% mercury vapour. The E/N and pressure ranges used were O� 2 to 1� 5 Td and 5�4 to 15�2 kPa for pure mercury vapour, 0 �08 to 3�0 Td and 5 �40 to 26�88kPa for the mixture containing helium and 0�06 to 5�0Td and 3�33 to 16�67kPa for the mixture containing nitrogen. It is shown that the use of mixtures significantly reduces the dependence of the measured drift velocity on the pressure, due to the effect of mercury dimers, from that measured in pure mercury vapour. An iterative procedure to derive the momentum transfer cross section for electrons in mercury vapour over the range 0�04 to 4 eV with an uncertainty between �5 and 10% is described. It is concluded that previously published momentum transfer cross sections for mercury vapour derived from drift velocity data are significantly in error, due to diffusion effects and the procedure used to correct for the influence of dimers. The present cross section is in good agreement with the semi-empirical calculations of Walker (personal communication).

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