The multiphoton ionization spectrum of t r a n s-1,3-butadiene

Abstract

The multiphoton ionization spectrum of trans‐1,3‐butadiene has been measured from dye laser wavelengths of 365 to 468 nm using an intensity‐corrected system. In the four‐photon ionization region to lower energy than 405 nm, many three‐photon resonances with Rydberg states are seen and a new series with a quantum defect of 0.04 is identified. The symmetries of the observed Rydberg series are discussed. Above 405 nm in energy, a resonance occurs with the ? state seen in one‐photon absorption spectra, only the structure in the multiphoton ionization spectrum is characteristic of an allowed two‐photon resonance. From the vibronic structure of this state, it is argued that it has symmetry ¹B_g. In the region covered by this study (42 700 to 54 800 cm⁻¹ in two‐photon energy) no state was found to which a ¹A_g symmetry designation could be applied.