Harminv is a free program (and accompanying library) to solve
the problem of harmonic inversion, given a discrete-time,
finite-length signal that consists of a sum of finitely-many
sinusoids (possibly exponentially decaying) in a given bandwidth,
it determines the frequencies, decay constants, amplitudes,
and phases of those sinusoids.

Homepage:
https://github.com/NanoComp/harminv/blob/master/README.md
