Rationalization of experimental photoelectron spectra of the cyanocyclopentadienide anion (CpCN−) via vibronic coupling theory

Abstract

This work reports the vibronic coupling study of the first four electronic states of the cyanocyclopentadienide anion (CpCN⁻) including both adiabatic and nonadiabatic treatments. For adiabatic calculations, wave-packet–density maps are calculated to assign the vibronic lines. Whereas the non-adiabatic calculations capture from close electronic states, analysis of population transfer and conical intersection proximity with electronic states. The computed photoelectron spectrum reproduces the two experimental bands observed up to (4.0 eV) and, in addition, predicts two further features at substantially higher electron binding energies (≫6.5 eV). Together, these results clarify how vibronic and nonadiabatic couplings shape the detachment dynamics of CpCN⁻ and provide theoretically deduced spectra with two higher-energy peaks.