Line Narrowing And Matrix Site Effects In Condensed Phase Spectra. I. Fluorescence Spectra Of P-dfb In Cyclohexane. Ii. Nhbs Of Resorufin In Vitreous Matrices (para-difluorobenzene, Nonphotochemical Hole Burning-spectroscopy, H.b.s.).

The low temperature fluorescence spectra (4.2 K) of solid solutions of para-difluorobenzene-h(,4) and -d(,4) in cyclohexane have been recorded and analyzed. The absence of fluorescence from vibrationally excited states at 4.2 K eliminates the sequence and hot band structure which complicate the analysis of the vapor phase fluorescence spectrum. On the basis of a comparison of our vibrational analysis with those published for the vapor phase fluorescence, several incorrect assignments in the latter have been identified. The high resolution (< 1cm('-1)) and lack of spectral congestion in the low temperature matrix isolation fluorescence spectra also allowed additional vibrational assignments to be made. These results are of added importance because of the extensive use which has been made of para-difluorobenzene for radiationless relaxation studies in the vapor phase. Nonphotochemical hole burning and thermal annealing experiments have been conducted on the ionic dye resorufin in a matrix of polymethylmethacrylate. Hole refilling measurements confirm the nonphotochemical nature of the hole burning process in this material. The temperature dependence of the line shape of the nonphotochemical spectral hole was determined over the temperature range 2-70 K. The experimental data suggest that, under the conditions of the experiment, the line shape of the hole is determined predominantly by spectral diffusion. Isoabsorptive points were observed in the absorption spectrum of the sample during both hole burning and thermal annealing of spectral holes. A model has been developed for the dynamical behavior of resorufin in the vitreous PMMA polymer matrix. The model exhibits isoabsorptive behavior for certain special relationships between the dynamical parameters. Mechanisms for the hole burning and thermal annealing processes have been proposed which are consistent with these dynamical relationships. Two additional matrices: 4:1 ethanol/methanol and polyacrylic acid were also investigated as hosts for the resorufin dye.PhDPhysical chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/127748/2/8520882.pd