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Manuscript Title: Proion: a code for calculating ionisation threshold intensities and ionisation periods in high-intensity-laser irradiated plasmas.
Authors: B.W. Boreham
Program title: PROION
Catalogue identifier: AARY_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 27(1982)65
Programming language: Fortran.
Computer: UNIVAC 1108 AND 1100/42.
Operating system: EXEC - 8.
RAM: 373K words
Word size: 36
Keywords: Ionisation, Laser physics, Ionisation probability Function, High intensity, Tunneling.
Classification: 15.

Nature of problem:
The evaluation of ionisation threshold intensities (the minimum intensity at which ionisation will occur) and the ionisation period for irradiation of the test gas with intensities greater than the threshold intensities.

Solution method:
PROION calculates ionisation intensities and ionisation periods using the general theory of ionisation of Keldysh. The ionisation threshold intensity or ionisation period and intensity at which ionisation occurs for intensities greater than the threshold, are calculated by iteration using the Keldysh ionisation probability function for the input ionisation potential of the test gas, the laser beam minimum intensity and the laser beam pulse width.

Restrictions:
The calculation is restricted to the tunneling limit (strong field) case of the Keldysh general formula, although the program can be easily adapted to the other limiting case of multiphoton absorption (moderate electric fields). The calculation is restricted further to exclude Coulomb force corrections, since it is this case that agrees best with experiment. The laser wavelength is assumed to be 1.06 um, but the calculation is not strongly dependent on wavelength and may be readily adapted for lasers other than neodymium.

Unusual features:
PROION as in standard FORTRAN except for the input lists, which are in free format.