Programs in Physics & Physical Chemistry
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|Manuscript Title: EROTVIB: a general program to calculate rotationally and/or vibrationally elastic and inelastic cross sections for electron (positron) scattering by spherical, symmetric and asymmetric top molecules.|
|Authors: A. Jain, D.G. Thompson|
|Program title: EROTVIB|
|Catalogue identifier: AAJM_v1_0|
Distribution format: gz
|Journal reference: Comput. Phys. Commun. 32(1984)367|
|Programming language: Fortran.|
|Operating system: NOS 1.4.|
|RAM: 64K words|
|Word size: 60|
|Keywords: Spherical top, Symmetric top, Asymmetric top, Point group, Excitation vibrational, Rotational excitation, Scattering elastic, Adiabatic-nuclei Rotation (vibration) Approximations, K-matrix, T-matrix, Body-fixed frame, Closure formula, Total, Differential and Moment transfer Cross sections, Scattering, Electron, Molecule.|
Nature of problem:
This program calculates cross sections (total, differential and momentum transfer) for rotationally and/or vibrationally elastic and inelastic scattering of low energy electron (positron) impact by polyatomic molecules. It requires the body-fixed (BF) frame K-matrices for each symmetry (and at each geometry in case of vibrational excitation) as the input. For a polar molecule, the program has the provision to use the closure formula of Crawford and Dalgarno in order to obtain converged cross sections.
The BF frame scattering amplitude is first converted into space-fixed (SF) frame and then the Chase formula, in the adiabatic-nuclei-rotation (vibration) approximation, is employed to derive expressions for rotationally and/or vibrationally elastic and/or inelastic cross sections.
The program is designed to accept K-matrices only up to the maximum dimension of 22*22. This, in the context of present molecules, means that up to lmax=7 partial waves can be included in the calculation [ in this case, in eq. (1) LBIG=14]. At the same time, the maximum value of the final rotational quantum number (JF(I)) can be only up to 5. However, for JF(I)>5 and lmax >7, the program can easily be modified by changing dimensions of various arrays (described in the code).
For the present test case of e-H2O scattering the determination of AL coefficients for LBIG=7 [eq. (1)] takes only 0.2 s. In this calculation, the time to evaluate asymmetric top eigenfunctions is not included; however, this should again be less than one second.
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