Molcol: a program for solving atomic and molecular collision problems. D.R. Flower, G. Bourhis, J.-M. Launay.

PROGRAM SUMMARY
Title of program: MOLCOL
Catalogue identifier: ADMK
Ref. in CPC: 131(2000)187
Distribution format: tar gzip file
Operating system: UNIX (AIX 3.2.5, IRIX 6.5, SunOS)
High speed store required: 16MK words
Number of bits in a word: 32
Number of lines in distributed program, including test data, etc: 3420
Keywords: Molecular collisions, Rovibrationally inelastic scattering, Elastic, Quantal coupled channels method, Fine structure excitation.
Programming language used: Fortran
Computer: IBM RS6000 , SGI Origin 2000 , Sun E6500 .

Nature of physical problem:
Inelastic scattering between molecules and atoms possessing internal structure is studied in the laboratory and by means of observations of interstellar space. In order to interpret and analyze these measurements and observations, quantal scattering codes are required which compute inelastic cross sections as functions of the barycentric collision energy.

Method of solution
The partial wave expansion (quantal coupled channels) techinque is employed here. The Schrodinger equation is reduced to a set of coupled, first order differential equations, which are solved by numerical integration in the radial variable to obtain scattering matrices and cross sections. The interaction potential must be supplied in a specified functional form.
The program uses Lapack and Blas routines (for matrix algebra).

Restrictions on the complexity of the problem
The program treats collisions between two systems of arbitrary angular momenta, j1 and j2, where j=l+s. System 2 may be allocated an additional internal quantum number.

Typical running time
On an IBM RS6000 processor, the first test run (Section 4.1) requires 90 s, and the second test run (Section 4.2) requires 60 s.