Vibronic Structure and Photoelectron Angular Distribution in the Photoelectron Spectrum of ICN

In some molecular systems, the complex vibronic structure of photoelectron bands demand extensive theoretical and computational efforts to delineate the interactions between vibrational degrees of freedom and electronic motion, further complicated by coupling of orbital and spin momenta of the electrons. The photoelectron spectroscopy of ICN has been a very challenging problem that has received a lot of attention. However, a conclusive interpretation of the spectrum, in particular, the complex spin-vibronic structures of the B ²Π_3/2 and B ²Π_1/2 states, has remained elusive. In this presentation, we will explain the complex vibronic structure of ICN by analyzing the Dyson orbitals corresponding to the ionized electrons. The simulated spectra have been found to successfully reproduce the position and intensities of the main four photoelectron bands along with the associated vibronic structures. The shape resonances seen in the experimental asymmetry parameters and the trends of ionization cross-section with increasing electron kinetic energies are explained in terms of the partial wave analysis of the departing photoelectron and the contribution of allowed photoelectron angular momentum channels to the ensuing photoelectron wave function.