LEVEL: A computer program for solving the radial Schrödinger equation for bound and quasibound levels

- Efficient computer program for solving the radial or 1D Schroedinger equation.
- Automatically finds quasibound levels & calculates their widths (tunneling lifetimes).
- Can find all bound vibrational levels if any single-or double-minimum potential well.
- Can input and use potentials having a several analytic forms. or pointwise potential.
- Can incorporate with atomic-mass-dependent Born-Oppeheimer breakdown corrections.
- Calculates Bv and the first six centrifugal distortion constants for any/all levels.
- Calculates expectation values of various radial variables and of functions of them.
- For two potential functions, can generate line lists, FCFs and matrix elements.

This paper describes program LEVEL, which can solve the radial or one-dimensional Schrödinger equation and automatically locate either all of, or a selected number of, the bound and/or quasibound levels of any smooth single- or double-minimum potential, and calculate inertial rotation and centrifugal distortion constants and various expectation values for those levels. It can also calculate Franck-Condon factors and other off-diagonal matrix elements, either between levels of a single potential or between levels of two different potentials. The potential energy function may be defined by any one of a number of analytic functions, or by a set of input potential function values which the code will interpolate over and extrapolate beyond to span the desired range.