Photochemistry of Chloropentafluoroacetone

Abstract

<p> When chloropentafluoroacetone in the gas phase at room temperature is electronically excited in the ultraviolet region, emission is observed. This emission is assigned to a transition from the 1 (n,π*) state. Deactivation of the vibrationally excited singlet state can occur when the ketone is excited at short wavelengths. The internal heavy atom effect on both radiative and radiationless transitions from the excited singlet state is relatively small. The quenching of the chloroketone molecules in the zeroth vibrational level of the excited singlet state has been studied and the probable quenching mechanisms proposed. Intersystem crossing from the excited singlet state to the triplet state is an important process in the gas phase at room temperature. However, phosphorescence is observed only in matrices at low temperatures, e.g. 77°K. The internal heavy atom effect on radiative and radiationless transitions from the triplet state in the matrix at low temperature is small. </p>