Elsevier Science Home
Computer Physics Communications Program Library
Full text online from Science Direct
Programs in Physics & Physical Chemistry
CPC Home

[Licence| Download | New Version Template] aaga_v1_0.gz(15 Kbytes)
Manuscript Title: A program for calculating Regge trajectories in potential scattering.
Authors: P.G. Burke, C. Tate
Program title: REGGE TRAJECTORY
Catalogue identifier: AAGA_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 1(1969)97
Programming language: Fortran.
Computer: I.C.L.1907.
Operating system: QUBE.
RAM: 11K words
Word size: 24
Keywords: Nuclear physics, Phase shift, Bound state, Regge, Bessel function, Eigenvalue, Schrodinger, Complex, Gamma function, Yukawa potential, Trajectory, S-matrix, Scattering, Pole, Angular momentum, Optical model.
Classification: 17.9.

Nature of problem:
This program solves the radial Schrodinger equation and finds the positions and residues of Regge poles for a Yukawa potential and follows these poles automatically as a function of energy. Alternatively, it will compute the S-matrix and phase shifts at a specified grid of points in the complex angular momentum plane and for a given set of energies. The program can be modified to calculate Regge trajectories for any potential which can be specified by an analytic formula.

Solution method:
The radial Schrodinger equation is integrated numerically inwards and outwards using the Runge-Kutta-Gill method. The S-matrix is determined by fitting the solution to a complex Bessel function, and the poles in the S-matrix are found by Newton's iteration method.

Restrictions:
The program is limited to real positive and negative values of the energy and to all complex angular momenta except the half odd integers.

Running time:
The evaluation of the S-matrix at one point takes about six seconds on the ICL 1907. To determine the position of a pole in the S-matrix takes about 40 seconds for a typical number of iterations.