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Manuscript Title: Real and imaginary part of the heavy ion optical potential from a realistic nucleon-nucleon interaction.
Authors: A. Faessler, L. Rikus, R. Sartor
Program title: RIHIOP
Catalogue identifier: ABPL_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 28(1983)275
Programming language: Fortran.
Computer: UNIVAC 1100.
Operating system: EXEC LEV. 37R2A.
RAM: 33K words
Word size: 32
Keywords: Nuclear physics, Volume and surface Contributions, Complex optical Potential, Optical model.
Classification: 17.9.

Nature of problem:
The program calculates the volume and surface contribution to both the real and imaginary parts of the optical potential between two heavy ions. The volume part is computed by a double folding procedure which uses a complex effective force as input while the surface part is obtained as the second order term of the Feshbach expression by taking explicitly into account the excitation of a set of intermediate vibrational states.

Solution method:
Volume part: The volume part can be written as a five-dimensional integral which is calculated numerically using Gaussian quadrature. Surface part: The surface part is written as a sum over contributions from each surface excitation state. The related Greens Function is expanded in a local plane wave expansion involving a sum over partial waves. The localizing integral is calculated numerically using Gaussian quadrature.

Restrictions:
The number of ion-ion separation distances at which the optical potential can be computed is limited to 20. However, any increase of this limit can easily be implemented. The projectile momentum is limited to less than 0.5 fm**-1/nucleon. For the surface contributions only isoscalar vibrational states of multipolarity Chi= 2, 3, 4 are allowed. Isovector states of lambda = 1, 2, 3, 4 can be included if the Coulomb excitation mechanism is turned on. A total of 10 excitation states only can be included (20 if the two heavy ions are identical). The heavy ions are restricted to even mass nuclei with ground state angular momentum zero.

Running time:
The calculation of the grid of values of the volume potential required as input for the surface excitation subprogram takes approximately 5 min for each of the test examples. For each point required by the user an additional 40 s should be allowed for.