Electronic Structure and Spectra of Acrylic Acid in the Vapor and Condensed Phases

Abstract
Near and vacuum UV absorption spectra of acrylic acid were measured at room temperature in the vapor phase and at 77 K in the condensed phase. From a comparative study of the observed spectra, a Rydberg excitation band was observed at 7.46 eV in addition to valence-shell transition bands. The estimated value of the quantum defect (δ=1.01) indicates that the Rydberg orbital is 3s. A new modified CNDO-CI method applicable to planar molecules was developed and applied to acrylic acid to investigate the valence-shell transitions, the observed bands at ∼5.0 and 6.71 eV being assigned to the transitions to the n-π* and π-π*, respectively.