So I'm doing research on a particular protein and I need to find bond lengths to parameterize the chromophore. I currently have a bunch of IR Spectroscopic data and I'm thinking I can use the wavelengths of absorptions between bonds to somehow find bond length. I am actually a physicist and so anything regarding the molecular physics of this would be helpful. Also If I can't calculate bond lengths, I might need to do an "AB Initio QM" calculations of the bonds. Would you have any good sources on how this is done and what software I can use?