Electronic states of dibenzo-p-dioxin. A synchrotron radiation linear dichroism investigation

Abstract

The UV absorbance bands of dibenzo-p-dioxin (dibenzo-1,4-dioxin, DD) are investigated by synchrotron radiation linear dichroism (SRLD) spectroscopy on molecular samples aligned in stretched polyethylene. The investigation covers the range 58,000–30,000 cm−1 (170–330 nm), thereby providing new information on the transitions of DD in the vacuum UV region. The observed polarization data enable experimental symmetry assignments of the observed transitions, leading to revision of previously published assignments by Ljubić and Sabljić (J. Phys. Chem. A 109 (2005) 8209-8217). In general, the experimental spectra are well predicted by the results of quantum chemical calculations using time-dependent density functional theory (TD–DFT). The observed absorbance in the region 58,000–55,000 cm−1 (170–180 nm) in the vacuum UV is almost entirely short-axis polarized, in pleasing agreement with the predicted spectrum.