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Manuscript Title: Energy level calculations in Davydov model.
Authors: S.M. Abecasis, F.R. Femenia, E.S. Hernandez
Program title: ENERGY LEVELS IN DAVYDOV MODEL
Catalogue identifier: ABOE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 2(1971)33
Programming language: Fortran.
Computer: BULL GENERAL ELECTRIC625.
Operating system: GECOS.
RAM: 9K words
Word size: 36
Keywords: Nuclear physics, Excitation energies, Energy ratios, Davydov model, Davydov-chaban model, Bessel interpolation Formula, Newton-raphson method, Regula falsi method, Half-interval search, Gamma function, Collective model.
Classification: 17.20.

Nature of problem:
The program is designed to calculate collective excitations and energy level ratios with the Davydov model in terms of the three parameters alpha, mu and gamma0.

Solution method:
Bessel formula is used to interpolate the energy levels predicted by the Davydov-Filippov model. Newton-Raphson is applied to find the root of a fourth degree equation. A transcendental equation is solved either by the regula falsi or the half-interval search methods. The gamma function Gamma(x) is evaluated either with the Stirling series expansion or a seventh degree polynomial, according to the value of the argument

Restrictions:
This program can be used for a wide range of the parameters aplha, mu and gamma0 fulfilling the conditions 8degrees <= gamma0 <= 30degrees and 0 <= mu <= 1. Computations are performed with the energy levels of the ground state rotational band from I=0 up to 20 (by steps of 2) and those of the anomalous band for I=2 up to 10 (by steps of 1) of the Davydov- Filippov model.

Unusual features:
Successive level sequences can be performed in the same run. Essentially the same algorithm described here may be used to search the best value for the model parameters. This program allows one to compute energy levels and their ratios in Davydov-Chaban model, with a minimum of alternatives.

Running time:
The test run for one nucleide takes about 8 minutes for compilation and 22 s for execution.