# Software for computations of rovibrational states' energies and corresponding spectroscopic constants in diatomic molecules

I need to compute rovibrational energy levels and also the spectroscopic constants, especially $$\omega_e$$ to compare my results with other papers.

So far I've tried LEVEL16, which seems very promising, but, unfortunately, it seems, that it provides just some of the constants, as described in How to obtain spectroscopic constants Omega_e, Alpha_e, B_e, D_e and D_0 from centrifugal constants?.

Also I've tried Psi4 and Molcas Vibrot, but none of them is able to fit my potential energy curves precisely enough and contrary to LEVEL16 they don't provide parameters to modify interpolation behavior.

Finally I've tried Duo, but I found out, that it isn't able to compute rovibrational energy levels and constants from point-wise computed function as described in this issue.

Do you know any other software, which could be used to compute both the rovibrational energy levels AND the spectroscopic constants including $$\omega_e, \alpha_e, B_e, D_e$$ and $$D_0$$?

• "To compare my results with other papers." Do they compute them somehow? – pH13 - Yet another Philipp Apr 29 at 17:47
• @pH13-YetanotherPhilipp They do, indeed. The problem is, that in one paper I'd like to use is no mention of a software used to compute them - authors probably implemented it themselves. – Eenoku Apr 29 at 17:50
• Why not write them to ask? :) – pH13 - Yet another Philipp Apr 29 at 18:01
• Well, that's not a bad suggestion :-) – Eenoku Apr 29 at 18:03