A theoretical study of vibronic coupling in the photoelectron spectra of Al 6 N .

This work emphasizes the appearance of non-adiabatic effects in the photoelectron spectra of Al 6 N - . It includes ab initio electronic structure calculations obtained on the first seven low-lying electronic states of Al 6 N - and a nuclear dynamics study utilizing time-dependent and time-independent quantum chemistry approaches. A model vibronic Hamiltonian is constructed in a diabatic electronic representation to estimate the coupling parameters corresponding to the fifteen vibrational modes of Al 6 N - . Theoretical spectral bands are achieved by employing the vibronic coupling theory followed by reduced dimensional calculations to understand the role of individual vibrational modes in the overall photoelectron spectra. Finally, the theoretically obtained photodetachment spectra show good agreement with the experimental spectra revealing vibronic coupling among the closely spaced spectral bands.