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Manuscript Title: Numerical modelling of a chemical plasma. I. REACS: a program to generate all reactions which take place in a plasma of given chemical content.
Authors: S.A. Roberts
Program title: REACS
Catalogue identifier: ACZD_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 18(1979)353
Programming language: Fortran.
Computer: ICL 1906A.
Operating system: GEORGE 4.
RAM: 15K words
Word size: 48
Peripherals: disc.
Keywords: Chemical reactions, Rate coefficients, Gas laser, Plasma physics, Laser physics, Atomic process.
Classification: 15, 19.1.

Subprograms used:
Cat Id Title Reference
ACZF_v1_0 DATSTOR CPC 18(1979)377

Nature of problem:
With the specific end in view to predicting the build up of secondary chemical species in the discharge tube of gas lasers, REACS is a program designed to generate all chemical reactions which could take place in such a plasma tube. These reactions provide input to a further code PLASKEM which solves the ordinary differential equations which describe the time rate of change of the chemical species. Options exist in REACS for the generation of reactions involving electrons and negative and/or positive ions.

Solution method:
For each possible set of integer ratios N1:N2:...:Nm of the elemental constituents of the plasma (subject to input restrictions), the program generates the array (N1,...,Nm). The array (N1,...,Nm) is split into all possible sets of three arrays, (n1(1),...,nm(1),...,(n1(3),...,nm(3) which together add vectorially to (N1...,Nm), and represent the three possible initial or final neutral molecules in a reaction. Neutral molecule reactions are formed by pairing all distinct sets of 3-arrays originating from the same parent (N1,...,Nm). Note that one or two of the arrays n(1), n(2) and n(3) may be null. Separate subroutines are written to generate from the neutral molecule reactions all types of reaction involving electrons, and negative and positive ions. In order to reject reactions involving molecules which are chemically unstable, a list of "allowed" molecules is provided as input to the code.

Restrictions:
The model does not take into account possible excitation of molecules during the reactions. Reactions involving cluster ions are not generated.

Running time:
60 s on ICL 1906A.