Spectroscopic study of Michler's ketone. Part 1.—Absorption

Abstract

It is shown that the near ultraviolet absorption band of Michler's ketone covers three electronic transitions. There are two ππ^* transitions, an intense one polarized perpendicular to the dipole moment and a weaker one at higher energy polarized parallel to the dipole moment, and an nπ^* transition polarized parallel to the dipole moment. For the ππ^* transitions the change of dipole moment upon excitation has been determined as 5.8 ± 0.5 and 3 ± 1 Debye, respectively. Whereas the nπ^* state appears to be the first excited singlet state in non-polar media, it becomes the third excited singlet state in ethanol. The change of the absorption spectrum with temperature is discussed.