Full-dimensional investigation of the photoionization spectrum of benzonitrile

The present investigation employs the state-of-the-art ab initio electronic structure and quantum dynamical method to examine the photoionization spectrum of benzonitrile (BN), also called cyanobenzene. A multi-state and multi-mode vibronic coupling model is developed and employed for the purpose. Utilizing both multi-configuration time-dependent Hartree (MCTDH) and its multi-layer (ML-MCTDH) variant, the dynamics and spectral feature of the BN radical cation (BN·+) are examined. The findings from the present theoretical work in conjunction with experimental photoionization spectroscopy aids to the understanding of complex interplay of electronic structural features and nuclear dynamics of this molecular system. This approach not only elucidates crucial features of individual photoionization bands of BN but also sheds light on the discrepancies of previous studies, as revealed by the reported spectral features. The results contribute further to the understanding of BN's potential applications in various dimensions, highlighting its unique electronic properties influenced by the cyano group. A strong correlation was found between the full dimensional ML-MCTDH findings, the experiment, and reduced dimensional MCTDH calculations. This indicates that the ML-MCTDH method is very efficient, which enabled understanding the finer details of spectral and dynamical features.