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Manuscript Title: The two-nucleon effective-range parameters with tensor forces.
Authors: L. Lovitch, S. Rosati
Catalogue identifier: ABGJ_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 4(1972)138
Programming language: Fortran.
Computer: IBM 7090.
Operating system: IBSYS VERSION 13.
RAM: 23K words
Word size: 36
Keywords: Nuclear physics, Schrodinger equation, Zero energy scattering, Effective range, Two-nucleon, Tensor forces, Scattering length, Neutron-proton, Wavefunctions, Nuclear reaction.
Classification: 17.8.

Subprograms used:
Cat Id Title Reference
ABGE_v1_0 DEUT CPC 2(1972)353
ABGE_v1_0 0001 CPC 4(1972)140

Nature of problem:
Subroutine EFRNG is a Fortran IV subroutine designed to calculate the zero energy wavefunction of the neutron-proton J=1+ state when the interaction between the particles is described by a given combination of central, tensor and spin-orbit potentials with or without a hard- core. From this one derives the effective range parameters, viz. The scattering length and effective range in terms of which can be expressed the low energy scattering behaviour. This subroutine may also be employed in the research of phenomenological potentials where a rapid and accurate calculation is required.

Solution method:
The problem is similar to that of obtaining the bound state solution of the two-nucleon Schrodinger equation in the presence of tensor forces presented in Comp. Phys. Commun 2(1971)353., and several of the subroutines which formed part of the program DEUT (Catalogue number: ABGE) are used by the present program. The technique used involves a direct numerical integration of the differential equations; the requirement that the wavefunctions vanish at the origin, that they behave asymptotically in an analytically well- determined way together with the employment of middle point matching determines the wavefunctions of the zero energy state uniquely.

The interparticle potentials considered in the program are those used in the above mentioned, namely Hamada-Johnston potentials and the Reid hard-core or soft-core potentials. To use EFRNG (or DEUT) in the case of some other potential one must simply re-write the subprogram POT.

Running time:
The test case requires 65 s to compile and 6 s to run on the IBM 7090 computer at Pisa University.