Knowledge Bank

As part of a continuing invesigation of the electronic structure of the polyenes [See L. J. Parkhurst and B. G. Anex, J. Chem. Phys. 45, 862 (1966)] a study of the single-crystal spectra of all-trans $\beta$-carotene is in progress. The room temperature and liquid-hydrogen temperature polarized specular reflection spectra obtained in this work will be presented here. The absorption spectra which result from Kramers-Kronig analyses of the reflection data will also be presented. The interpretation of these absorption curves leads to the absolute assignment of the electronic transitions lying in the visible and quartz ultraviolet. These results will be discussed in terms of the various models that have been proposed for the electronic structure of the polyenes.