Unusual geometries and spectroscopic properties of electronic states of In2N2

Twenty electronic states of In2N2 are computed using a complete active space multi-configuration self-consistent field followed by multi-reference singles + doubles configuration interaction (MRSDCI) computations. In contrast to other III–V tetramers, In2N2 exhibits nearly degenerate T-shaped triplet states and linear In–In–N–N 3Σ− state. The 1Ag state with a rhombus structure was found to be 0.94 eV higher. Our computations show that anion photodetachment spectra of In2N2 could be substantially different from the spectra of Ga2P2 and related tetramers observed by Neumark and coworkers. The computed vibrational and Raman spectra are provided.