Spectroscopic characterization on the neutral excited state and cationic ground state of styrene

•Vibrational frequencies of neutral excited state S1 and cationic ground state D0 of styrene were accurately measured.•The experimetal and theoretical results reveal that the geometry of styrene in S0, S1 and D0 maintains planarity.•PADs obtained in SEVI spectra suggest that no apparent threshold shape resonance occurs in the ionization of styrene.

The spectroscopic properties of styrene have been investigated via resonance-enhanced multiphoton ionization (REMPI) and slow electron velocity-map imaging (SEVI) methods. Vibrational frequencies in the first excited state of neutral (S1) and ground electronic state of cation (D0) have been accurately measured. From the one-color REMPI spectrum of styrene, the S1 ⟵ S0 electron transition energy is determined as 34729 ± 3 cm−1. Most low-frequency vibrations of S1 state are unambiguously identified with the aid of calculated results at TD-B3LYP/6–311 + +G(d, p) level. Some controversially high-frequency vibrational modes of S1 state are reassigned in comparison with theoretical results. The SEVI spectra taken via various S1 intermediate levels provide the detailed vibrational structures of D0 state and directly yield the accurate adiabatic ionization potential (IP) of 68267 ± 6 cm−1. The vibrational frequencies of the D0 state calculated at the B3LYP/6–311 + +G(d, p) level are in excellent agreement with the experimental results to aid us assigning some high-frequency vibrational modes.

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