<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> / Thesis / Doctor of Philosophy (PhD)

This work focuses on finding the complete iodine and nitrogen nuclear electric quadrupole coupling tensors for fluoroiodoacetonitrile using chirped-pulse Fourier transform microwave spectroscopy. Fluoroiodoacetonitrile contains two hyperfine nuclei, iodine (I=5/2) and nitrogen (I=1) and the spectra were observed with great resolution. A total of 499 transitions were observed for this molecule. The a, b and c rotational constants were obtained. A study of chloropentafluoroacetone was also done using chirped-pulse Fourier transform microwave spectroscopy. The two chlorine isotopes for this molecule, Cl-35 and Cl-37 were observed and 326 and 170 transitions were recorded, respectively.