LSFBTR

LSFBTR: A subroutine for calculating spherical bessel transforms. Nature of problem: Transforming an angular momentum wave function from coordinate to momentum representation requires the calculation of Hankel transforms for spherical Bessel functions. This subroutine calculates such integrals when the function to be transformed is given numerically at r values that are distributed uniformly in the variable ln(r). The resulting values of the transform are given at k values distributed uniformly in the variable ln(k). Solution method: The transform can be carried out as two successive Fourier transforms that are calculated numerically using the trapezoidal rule. For meshes with a large number of points these can be calculated very efficiently using the fast Fourier transform method.