The ezSpectra suite: An easy-to-use toolkit for spectroscopy modeling
A molecule's spectrum encodes information about its structure and electronic properties. It is a unique fingerprint that can serve as a molecular ID. Quantum chemistry calculations provide key ingredients for interpreting spectra, but modeling the spectra rarely ends there; it requires additional steps that entail combined treatments of electronic and nuclear degrees of freedom and account for specifics of the experimental setup (light energy, polarization, averaging over molecular orientations, temperature, etc.). This Software Focus article describes the ezSpectra suite, which currently comprises two stand-alone open-source codes: ezFCF and ezDyson. ezFCF calculates Franck-Condon factors, which yield vibrational progressions for polyatomic molecules within the double-harmonic approximation. ezDyson calculates absolute cross-sections for photodetachment/photoionization processes and photoelectron angular distributions using Dyson orbitals computed by a quantum chemistry program.