# A new Fortran program for the 9-j angular momentum coefficient

## Description

Abstract The simplest known form for the 9-j angular momentum coefficient, due to Jucys-Bandzaitis, has been identified as a particular case of the triple hypergeometric functions of Lauricella-Saran-Srivastava. This triple-sum series forms the basis for a new Fortran program for the numerical calculation of the 9-j angular momentum coefficient, which is faster and better than the program based on the conventional single sum (over one product of three 6-j coefficients) expression for the 9-j coefficie... Title of program: NINEJ Catalogue Id: ABLE_v1_0 Nature of problem The program calculates the 9-j coefficient (also called as the ls-jj transformation coefficient), using the single sum formula or the triple- sum formula due to Jucys and Bandzaitis. This coefficient arises in the recoupling of four angular momenta, which can be coupled either using the Russell-Saunders scheme or the jj-coupling scheme. It is of fundamental importance in the evaluation of matrix elements which occur in nuclear, atomic and molecular physics calculations. Versions of this program held in the CPC repository in Mendeley Data ABLE_v1_0; NINEJ; 10.1016/0010-4655(89)90021-0 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019)