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STRUCTURE AND EXCITED-STATE DYNAMICS OF AROMATIC NITRILES IN SUPERSONIC FREE JET

Campos Ramos, Ricardo E.
http://rave.ohiolink.edu/etdc/view?acc_num=akron1132244275

Abstract Details

2005, Doctor of Philosophy, University of Akron, Chemistry.
Excitation-energy dependence of fluorescence intensity and lifetime has been measured for 4-dimethylaminobenzonitrile (DMABN), 4-aminobenzonitrile (ABN), 4-diisopropylaminobenzonitrile (DIABN) and 1-cyanonaphthalene (1CNN) in a supersonic free jet. In all cases, the fluorescence yield decreases rather dramatically, whereas the fluorescence lifetime decreases only moderately for ( ) excess vibrational energy exceeding about 1000cm-1. This is confirmed by the normalized fluorescence excitation spectrum with the absorption spectrum of the compound in the vapor phase. The result indicates that the strong decrease in the relative fluorescence yield at higher energies is due mostly to a decrease in the radiative decay rate of the emitting state. Comparison of the experimental results with the Time Dependent Density Functional Theory (DDFT) potential energy curves for excited states strongly suggests that the decrease in the radiative decay rate of the amino-benzonitriles at higher energies is due to the crossing of the singlet state by the lower-lying singlet state of very small radiative decay rate. The threshold energy for the fluorescence “break-off” is in good agreement with the computed energy barrier for the crossing. For 1CNN, on the other hand, the observed fluorescence break-off can be best attributed to the crossing of the singlet state by the triplet state. A concerted experimental (mass-selective spectroscopy) and theoretical (correlated quantum chemistry calculation) study of hydrogen-bonded clusters of 1-cyanonaphthalene (1CNN) with water has been carried out to probe geometries of the conformational isomers. The structures of the two low-energy conformers of 1CNN(H2O) and 1CNN(H2O)2 predicted by MP2/cc-pVDZ calculation, are consistent with ionization-loss (ion-dip) infrared spectra of C-H and O-H stretches of the two conformers, identified by ionization-detected hole-burning spectroscopy. The facile loss of a neutral water molecule from the cluster ion of 1CNN(H2O)2, relative to that of 1CNN(H2O), is in accord with the proposed structures of the complexes. Mass selected resonant two-photon ionization (R2PI) and ion-dip infrared spectroscopies are combined with correlated (MP2) quantum chemistry to probe electronic spectra and ground-state of jet cooled dimer and higher clusters of 1-cyanonaphthalene. The results indicate that the dimer has stacked geometries, consistent with the highly efficient excimer formation that follows photoexcitation of the ground-state clusters.
Edward Lim (Advisor)
137 p.
Chemistry, Physical
STRUCTURE AND DYNAMICS OF AROMATIC NITRILES; SUPERSONIC JET EXPANSION; LASER SPECTROSCOPY LIF MASS HIGH RESOLUTION SPECTROSCOPY

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Citations

  • Campos Ramos, R. E. (2005). STRUCTURE AND EXCITED-STATE DYNAMICS OF AROMATIC NITRILES IN SUPERSONIC FREE JET [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1132244275

    APA Style (7th edition)

  • Campos Ramos, Ricardo. STRUCTURE AND EXCITED-STATE DYNAMICS OF AROMATIC NITRILES IN SUPERSONIC FREE JET. 2005. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1132244275.

    MLA Style (8th edition)

  • Campos Ramos, Ricardo. "STRUCTURE AND EXCITED-STATE DYNAMICS OF AROMATIC NITRILES IN SUPERSONIC FREE JET." Doctoral dissertation, University of Akron, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1132244275

    Chicago Manual of Style (17th edition)

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© 2005, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.