Prediction of the photoelectron spectra of C122 by computing Franck-Condon factors

The computation of Franck-Condon factors plays a key role for unraveling vibronic spectra and nonradiative process of molecules. In this work the photoelectron spectra of C122 were predicted by computing Franck-Condon factors. The equilibrium geometries and harmonic vibrational frequencies of five allotropes of C60C2C60 with dumbbell structures, including their cations and anions, were calculated at the B3LYP/6-31G(d) level. To facilitate the computation of Franck-Condon factors, a prescreening process for selecting transitions with stronger intensities was developed. The efficiency was further improved by rearranging the order of normal mode as the larger the maximum vibrational quantum number, the higher the order. The photoelectron spectra of C122- → C122 + e- and C122 → C122+ + e- were simulated. The simulated spectra are distinct for each molecule, indicating that the five allotropes of C122 can be identified by the experiment of photoelectron spectroscopy.