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Manuscript Title: PEAD: for the calculation of photoelectron angular distributions of linear molecules.
Authors: J. Tennyson, N. Chandra
Program title: PEAD
Catalogue identifier: AAXD_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 46(1987)99
Programming language: Fortran.
Computer: NAS 7000.
RAM: 152K words
Word size: 32
Peripherals: disc.
Keywords: Molecular physics, Scattering, Photon, Photoionisation, Photoelectron angular Distribution, Rotationally resolved, Adiabatic nuclei Approximation, Boltzmann distribution, Asymmetry parameter beta.
Classification: 16.6.

Nature of problem:
PEAD takes photoionisation dipoles and calculates rotationally averaged and rotationally resolved photoionisation cross section parameters sigma and beta. These are then used to give thermally averaged parameters simaQ, sigmaS, betaQ and betaS for a given initial temperature.

Solution method:
The photoionisation cross section parameters, Sigma and Beta, are calculated using the adiabatic nuclei approximation for transitions between a range of rotational states. These are then thermally averaged using a Boltzmann distribution of initial rotational states.

The program assumes the parent molecule is linear and that the whole system remains in a singlet spin state.

Running time:
Data dependent. For a 3 channel problem on the NAS 7000, about 40 sets of transition dipoles can be analysed per second.