scholarly journals Some Electron Collision Cross Sections of Call

1954 ◽  
Vol 7 (1) ◽  
pp. 22 ◽  
Author(s):  
JT Jefferies
Keyword(s):  
Cross Sections ◽  
Born Approximation ◽  
Electron Collision ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Collision Cross Sections ◽  
The Cross

The cross sections for electron collision excitation of the transitions 4S1/B-4PlIs and 4Ps/S in Call have been calculated using a distorted wave Born approximation. For electrons of energy 4 e y, the calculated values are respectively 6� 6TCa~ and 9� 9TCa~.

Rotationally inelastic collisions of orbitally degenerate molecules; maser action in OH and CH

1979 ◽  
Vol 368 (1732) ◽  
pp. 99-123 ◽  
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Open Shell ◽  
Inelastic Collisions ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
The Cross ◽  
Maser Action

The theory of rotationally inelastic collisions between orbitally degenerate diatomic molecules and open-shell atoms is developed. Because of the orbital degeneracy two or more electronic potential energy surfaces are involved. Matrix elements of the interaction Hamiltonian are given, hyperfine coupling in the diatomic molecule also being included. From these it is apparent th at the parity of the initial Λ -doublet level will influence the inelastic scattering cross section for poles of interaction λ such that λ ≥ 2 Λ .An expression is developed for state-to-state cross sections using the restricted distorted wave Born approximation. A set of branching coefficients is defined which allows the representation of the parity dependence of the cross section in a simple parametric form. The theory is applied to collisional pumping as an excitation mechanism for interstellar maser action of OH and CH through the inversion of Λ -doublet populations. H atoms, H 2 , He, H + and H + 3 are considered as collision partners. Branching coefficients are tabulated for a variety of excitations from the rotational ground states. The sense of the parity dependence of the cross sections arises from the gross features of the interaction potential at medium and long range, and can be deduced using approximate theoretical surfaces or empirical models. An analogy is drawn with the experimental rates of rotational energy transfer in the closely related system H + NH 2 (Ã, 2 A 1 ), which are ca. 10 -9 cm 3 s -1 , and which have been successfully interpreted using the distorted wave Born approximation. These results are used to give qualitative predictions of population inversion in the Λ -doublets of OH, OD and CH in interstellar clouds. We show th at the ground J = 1 ½ doublet, and excited doublets of the F 1 manifold, of OH and OD will be inverted following collisions with H, H 2 and He. The J = 1/2 doublet of the F 2 manifold of OH and OD will be inverted by collisions with the ions H + and H + 3 . In CH low temperature collisions with H atoms will result in inversion of the ground J = 1 ½ doublet. Collisions with H 2 and He at low temperature result in cooling of the doublet. Implications for maser action are briefly discussed.

Formal and Approximate Evaluations of a Number of Collision Integrals for Diatomic Molecules

1973 ◽  
Vol 28 (6) ◽  
pp. 824-834
Author(s):  
H. Moraal
Keyword(s):  
Simple Model ◽  
Cross Sections ◽  
Born Approximation ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Approximate Evaluation ◽  
Collision Integrals ◽  
Quadrupole Interactions ◽  
Collision Cross Sections ◽  
Law Of Corresponding States

Expressions which are exact in the distorted wave Born approximation are derived for a number of kinetic theory collision cross sections, viz. This is done for a number of nonspherical potentials, namely for single-P1 , single-P2, dipole-dipole, dipolequadrupole and quadrupole-quadrupole interactions. A number of additional approximations is used to obtain approximate relations between some of these cross sections and to derive a approximate law of corresponding states. A simple model is described which makes the approximate evaluation of collision cross sections for multipole-multipole interactions very straightforward.

Analysing powers and differential cross sections of (3He,p) reactions on 6Li and 7Li at low energy

1995 ◽  
Vol 73 (1-2) ◽  
pp. 74-84 ◽  
Author(s):  
D. Baddou ◽  
C. Rioux ◽  
R. J. Slobodrian ◽  
J. M. Nelson
Keyword(s):  
Cross Sections ◽  
Differential Cross ◽  
Born Approximation ◽  
Low Energy ◽  
Angular Distributions ◽  
Differential Cross Sections ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Nucleon Transfer ◽  
Cluster Transfer

Angular distributions of the differential cross sections and analysing powers were measured at an energy of 4.6 MeV. The results are compared with the distorted wave Born approximation predictions for two-nucleon transfer and for a deuteron-cluster transfer. The agreement is qualitative at best, and a discussion of alternatives to improve it is presented.

Zero-range distorted-wave Born approximation analysis of (p,t) transfer reactions

1981 ◽  
Vol 59 (2) ◽  
pp. 231-237 ◽  
Author(s):  
J. J. Bevelacqua ◽  
S. V. Prewett
Keyword(s):  
Form Factor ◽  
Cross Sections ◽  
Born Approximation ◽  
Surface Reaction ◽  
Target Surface ◽  
Transfer Reactions ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Zero Range ◽  
Approximation Analysis

Zero-range distorted-wave Born approximation calculations are used to investigate the systematics of two-nucleon transfer reactions. The shapes of the calculated 40Ca(t,p)42Ca(gs) and 208Pb(p,t)206Pb(gs) cross sections are relatively insensitive to details of the core plus two-neutron form factor, if the form factor tails have similar shapes. Studies of heavy targets such as 206Pb suggest a surface reaction mechanism, but lighter targets (16O and 40Ca) indicate that spatial regions beyond the target surface provide the dominant contribution to the (p,t) cross section.

Superoperator methods of calculating cross sections: II. Distorted wave Born approximation

1976 ◽  
Vol 54 (13) ◽  
pp. 1328-1342 ◽  
Author(s):  
R. F. Snider ◽  
R. E. Turner
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Correlation Functions ◽  
Born Approximation ◽  
Collision Cross Section ◽  
Internal State ◽  
Time Correlation ◽  
State Transitions ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation

The superoperator form of the collision cross section is evaluated within the distorted wave Born approximation. It is first verified that the obvious expansion methods give a result identical to that obtained by standard methods. Formalistically, the algebraic expansions of the transition operator and superoperator are shown to have parallel structures. The distorted wave Born approximation for the cross section also has a structure parallel to the structure of the Born approximation cross section. This is especially brought out by formulating the results in terms of time correlation functions. Certain simplifying features are found for cross sections averaged over initial and final velocity directions. These cross sections for internal state transitions are further simplified by averaging over a Maxwellian distribution of initial velocities in such a way as to obtain 'kinetic cross sections' appropriate for gas kinetic phenomena. Connection is also made with the 'constant acceleration approximation' used to estimate correlation functions in gas phase NMR.

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