Disorientation and disalignment of 42P3/2 potassium atoms, induced in resonant collisions

1980 ◽  
Vol 58 (10) ◽  
pp. 1500-1506 ◽  
Author(s):  
P. Skalinski ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Selective Excitation ◽  
Variable Magnetic Field ◽  
Constant Field ◽  
Resonance Fluorescence ◽  
Vapor Density ◽  
Scanning Method ◽  
Total Cross Sections ◽  
Circularly Polarized ◽  
Potassium Vapor

The total cross sections for disorientation (σ1) and disalignment (σ2) of 42P3/2 potassium atoms, induced in collisions with the ground-state atoms, have been determined using a modified Zeeman scanning method. Potassium vapor at densities of the order of 1011 cm−3, contained in a fluorescence cell located in a kilogauss variable magnetic field, was irradiated with circularly polarized 7665 Å resonance radiation emitted from a discharge lamp located in a constant field of 5.4 kG. Scans of the variable field permitted selective excitation of single Zeeman components in the absorbing vapor. The σ+ and σ− components of the resulting resonance fluorescence emitted parallel to the scanning field were monitored in relation to the vapor density, as were the π and σ components emitted in the perpendicular direction. As the vapor density increased so did the frequency of the collisions which caused transfers among the Zeeman states in the vapor and thus disorientation and disalignment. The observed dependence of circular and linear depolarization of the fluorescence on the potassium density yielded the cross sections σ1 = 17 × 10−12 cm2 and σ2 = 21 × 10−2 cm2, corrected for imprisonment of radiation.

Disorientation of 42P1/2 potassium atoms, induced in resonant collisions

1979 ◽  
Vol 57 (12) ◽  
pp. 2222-2226 ◽  
Author(s):  
P. Skalinski ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Variable Magnetic Field ◽  
Fluorescent Light ◽  
Exciting Light ◽  
Constant Field ◽  
Resonance Fluorescence ◽  
Resonance Transition ◽  
Vapor Density ◽  
Scanning Method ◽  
Potassium Vapor

A (modified) Zeeman scanning method was used to determine the cross sections for disorientation of potassium atoms in the 42P1/2 resonance substate, induced in collisions with the ground-state atoms. Potassium vapor at densities of the order of 1011 cm−3 placed in a variable magnetic field was irradiated with σ+ polarized resonance radiation of wavelength 7699 Å emitted from a discharge lamp located in a constant field of 5.4 kG. The σ+ and σ− components of the resonance fluorescence emitted at right angles to the direction of excitation were monitored in relation to the vapor density as the variable field was scanned to make the σ+ resonance transition in the absorbing vapor coincide with the σ+ component present in the exciting light. As the vapor density increased, so did the admixture of the σ− component in the fluorescent light, which arises from collisional mixing between the mJ = 1/2 and mJ = −1/2 Zeeman substates. The resulting depolarization curve yielded the disorientation cross section σ1 = 4.0 × 10−11 cm2.

Disorientation of K(42P1/2) Atoms, Induced in Collisions with Noble Gases

1975 ◽  
Vol 53 (15) ◽  
pp. 1499-1503 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Zero Magnetic Field ◽  
Degree Of Polarization ◽  
Low Density ◽  
Resonance Fluorescence ◽  
Circularly Polarized ◽  
Potassium Vapor ◽  
The Cross ◽  
Gas Pressures

The cross sections for disorientation of 42P1/2 potassium atoms, induced in collisions with noble gas atoms, have been determined in zero magnetic field by studying the depolarization of K(7699 Å) resonance fluorescence in relation to noble gas pressures. Potassium vapor at low density, mixed with a noble gas in a fluorescence vessel, was irradiated with circularly polarized 7699 Å potassium resonance radiation and the resulting resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions and yielded the following disorientation cross sections which are appropriately corrected for the effect of nuclear spin: K–He, 24 ± 4 Å2; K–Ne, 21 ± 3 Å2; K–Ar, 37 ± 5 Å2; K–Kr, 51 ± 7 Å2; K–Xe, 69 ± 9 Å2. The cross sections are significantly smaller than values obtained previously in kilogauss fields.

Disorientation of Cs(62P1/2) atoms, induced in collisions with noble gases

1976 ◽  
Vol 54 (7) ◽  
pp. 748-752 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Buffer Gas ◽  
Resonance Fluorescence ◽  
Circularly Polarized ◽  
Low Field ◽  
Good Agreement ◽  
Gas Pressures

The disorientation of 62P1/2 cesium atoms, induced in collisions with noble gas atoms in their ground states, was systematically investigated by monitoring the depolarization of cesium resonance fluorescence in relation to noble gas pressures. The Cs atoms, contained together with a buffer gas in a fluorescence cell and located in zero magnetic field, were excited and oriented by irradiation with circularly polarized 8943 Å resonance radiation, and the resonance fluorescence, emitted in an approximately backward direction, was analyzed with respect to circular polarization. The experiments yielded the following disorientation cross sections which have been corrected for the effects of nuclear spin: Cs–He: 4.9 ± 0.7 Å2; Cs–Ne: 2.1 ± 0.3 Å2; Cs–Ar: 5.6 ± 0.8 Å2; Cs–Kr: 5.8 ± 0.9 Å2; Cs–Xe: 6.3 ± 0.9 Å2. The results are in good agreement with most of the available zero-field and low-field data.

Coherence Transfer between the 2P1/2 and 2P3/2 States in Potassium, Induced in Collisions with Noble Gas Atoms and with Molecules

1973 ◽  
Vol 51 (4) ◽  
pp. 425-430 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Coherence Transfer ◽  
Circularly Polarized ◽  
Sensitized Fluorescence ◽  
Potassium Vapor ◽  
Simple Molecules

The transfer of coherence accompanying 42P1/2 → 42P3/2 transfer of excitation induced in collisions between 42P1/2 potassium atoms and noble gas atoms as well as some simple molecules, was studied in a series of sensitized fluorescence experiments. Mixtures of potassium vapor at 6 × 10−7 Torr with the various buffer gases were irradiated with circularly polarized D1(σ+) light and the relative intensities of the σ+ and σ− fractions of both the D1 and D2 fluorescent components were determined in relation to the pressures of the buffer gases. The experiments yielded the following cross sections for coherence transfer: K–He:1.7 Å2; K–Ne :0.8 Å2; K–Ar < 0.5 Å2; K–H2 :3.5 Å2; K–CH4 :7.0 Å2; K–CD4:7.7 Å2.

Sensitized fluorescence in vapors of alkali metals. XII. 42P1/2–42P3/2 mixing in potassium, induced in collisions with ground-state rubidium atoms

1969 ◽  
Vol 47 (2) ◽  
pp. 223-226 ◽  
Author(s):  
E. S. Hrycyshyn ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Alkali Metals ◽  
Resonance Radiation ◽  
Total Cross Sections ◽  
Sensitized Fluorescence ◽  
Rubidium Atoms ◽  
Partial Pressures ◽  
Potassium Vapor ◽  
Detailed Balancing

The total cross sections for collisions between excited potassium and unexcited rubidium atoms, leading to the transfer of excitation between the 42P states in potassium, have been determined in a sensitized fluorescence experiment. The experiments were carried out at partial pressures of potassium vapor lower than 10−5 mm Hg, at which the imprisonment of resonance radiation may be disregarded. The cross sections Q12″ (42P1/2 → 42P3/2) and Q21″ (42P1/2 ← 42P3/2) equal 260 Å2 and 175 Å2, respectively, and are in the ratio predicted by the principle of detailed balancing.

Disorientation of Na(32P1/2) Atoms, Induced in Collisions with Noble Gases

1974 ◽  
Vol 52 (20) ◽  
pp. 1956-1960 ◽  
Author(s):  
B. Niewitecka ◽  
T. Skaliński ◽  
L. Krause
Keyword(s):  
Circular Polarization ◽  
Cross Sections ◽  
Nuclear Spin ◽  
Noble Gas ◽  
Gas Pressure ◽  
Degree Of Polarization ◽  
Low Density ◽  
Resonance Fluorescence ◽  
Sodium Vapor ◽  
Circularly Polarized

The cross sections for disorientation of 32P1/2 sodium atoms, induced in collisions with noble gas atoms, have been determined by following the depolarization of Na–D1 resonance fluorescence in relation to noble gas pressure. Sodium vapor at low density, mixed with a noble gas in a fluorescence cell, was irradiated with circularly polarized D1 resonance radiation and the resulting D1 resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions, and yielded the following disorientation cross sections which are appropriately corrected for effects due to nuclear spin. Na–He: 28.1 ± 4.0 Å2; Na–Ne: 27.8 ± 4.0 Å2; Na–Ar: 57.0 ± 8.0 Å2; Na–Kr: 78.0 ± 10 Å2; Na–Xe: 87.0 ± 13 Å2.

Sensitized fluorescence in vapors of alkali metals. XI Energy transfer in potassium–rubidium collisions

1969 ◽  
Vol 47 (2) ◽  
pp. 215-221 ◽  
Author(s):  
E. S. Hrycyshyn ◽  
L. Krause
Keyword(s):  
Energy Transfer ◽  
Cross Sections ◽  
Alkali Metals ◽  
Inelastic Collisions ◽  
Rubidium Vapor ◽  
Total Cross Sections ◽  
Sensitized Fluorescence ◽  
Rubidium Atoms ◽  
Transfer Processes ◽  
Potassium Vapor

Sensitized fluorescence in rubidium vapor, induced by collisions with excited potassium atoms, was investigated to determine the total cross sections for inelastic collisions between excited potassium atoms and rubidium atoms in their ground states. The collision cross sections for the various excitation transfer processes are as follows: Q12′ (K42P1/2 → Rb52P3/2) = 40 Å2, Q22′ (K42P3/2 → Rb52P3/2) = 27 Å2, Q11′ (K42P1/2 → Rb52P1/2) = 2.7 Å2, and Q21′ (K42P3/2 → Rb52P1/2) = 1.9 Å2. The partial pressure of potassium vapor in the K–Rb mixture was kept largely below 10−5 mm Hg to eliminate effects due to the trapping of potassium resonance radiation.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

scholarly journals Total cross sections of eγ → $$ eX\overline{X} $$ processes with X = μ, γ, e via multiloop methods

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Roman N. Lee ◽  
Alexey A. Lyubyakin ◽  
Vyacheslav A. Stotsky
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Elliptic Integral ◽  
High Energy ◽  
Calculation Methods ◽  
Complete Elliptic Integral ◽  
Total Cross Sections ◽  
Multiloop Calculation ◽  
The Cross ◽  
Analytical Expressions

Abstract Using modern multiloop calculation methods, we derive the analytical expressions for the total cross sections of the processes e−γ →$$ {e}^{-}X\overline{X} $$ e − X X ¯ with X = μ, γ or e at arbitrary energies. For the first two processes our results are expressed via classical polylogarithms. The cross section of e−γ → e−e−e+ is represented as a one-fold integral of complete elliptic integral K and logarithms. Using our results, we calculate the threshold and high-energy asymptotics and compare them with available results.

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