Excited states of trans-stilbene and 1,4-diphenylbutadiene. Near and vacuum UV polarization spectroscopy

The UV absorbance spectra of trans-stilbene ((E)-1,2-diphenylethene, DPE) and (E,E')-1,4-diphenyl-1,3-butadiene (DPB) are investigated by Synchrotron Radiation Linear Dichroism (SRLD) spectroscopy using stretched polyethylene as an anisotropic solvent. The investigation covers the range 58,000-25,000 cm-1 (172-400 nm). The observed polarization data provide information on the transition moment directions of the observed spectral features. The wavenumbers, intensities, and polarization directions of the observed spectral bands are compared with the results of quantum chemical calculations using the semiempirical all-valence-electrons method LCOAO and Time-Dependent Density Functional Theory (TD-DFT) with the functional CAM-B3LYP.