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Spectroscopy and Dynamics of Weakly-bound Anions Using Full- and Reduced-dimensional Theoretical Models

Horvath, Samantha

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Chemistry.
Reduced-dimensional theoretical models are used to study the vibrational structure and dynamics of weakly-bound anionic systems. In the first part of the work presented here, the low frequency vibrational modes (< 2000 cm –1) of X (H2O) species (X = F, Cl, Br, and I) are investigated using one- and two-dimensional models. In some cases a one-dimensional treatment works well at capturing the anharmonic motions of these systems, such as the out-of-plane bend. In other cases, mode-mode coupling must be included, either explicitly through a two-dimensional treatment or through inclusion of zero point energies in the other degrees of freedom. To test the veracity of these methods and proposed mechanisms, comparisons are drawn to relevant experimental studies and through isotopic substitution of the solvent molecule: H2O, HDO, and D2O. In the F (H2O) system, a two-dimensional treatment is employed to study both the OF and OHb stretches. In doing so, quantitative agreement with experiment is achieved and the extent of proton transfer promoted through vibrational excitation is examined. The extent of proton transfer is over 45% for states with one or more quanta of excitation in the OHb stretch. For examination of the in- and out-of-plane bend, investigations of the intensity patterns reveal that electrical anharmonicity is a key player in the anomalously large intensity in 2νoop, but similar intensity patterns in 2νip are not observed. In the second part, the photoinduced dissociation dynamics of anions is examined, both with and without the presence of a solvating molecule. Similar reduced-dimensional methods as those for X (H2O) are utilized but high level ab initio calculations (MR-SO-CISD) and full quantum dynamics are also employed. For IBr the robustness of previous classical analyses of this system are tested by solving the time-dependent Schr ödinger equation with the inclusion of temporal pulse information. Results of these calculations show that while there are some effects related to pulse width for short delay times (Δt < 500 fs), the majority of the structure in the spectra reflects the difference in potential energies between the anion and neutral surfaces at a particular I⋅⋅⋅Br separation with all of the excited molecules dissociating to form I + Br. For solvated molecular ions, the role of solvent orientation in promoting or hindering dissociation are investigated in Cu(CD3OD) and IBr(CO2) systems. In IBr(CO2) the presence of a single solvent molecule is enough to induce two additional channels. One of the channels is the electron transfer channel where the charge hops from I to Br when the IBr distance is ∼ 7 Â. This observation is investigated and interpreted by analyzing the change in the IBr electronic structure due to the presence of CO2. In a companion study on Cu(CD3OD), the effects of the couplings between the solvent internal degrees of freedom and the molecular (Cu⋅⋅⋅CD3OD) dissociation coordinate are investigated using a reduced-dimensional treatment. From these results, comparisons are drawn to earlier studies on Cu (H2O), and from which the effects of substituent substitution on the dissociation dynamics are discussed.
Anne McCoy, Dr. (Advisor)
Terry Miler, Dr. (Committee Member)
Christopher Hadad, Dr. (Committee Member)
Donna McCarthy Beckett, Dr. (Committee Member)
271 p.

Recommended Citations

Citations

  • Horvath, S. (2010). Spectroscopy and Dynamics of Weakly-bound Anions Using Full- and Reduced-dimensional Theoretical Models [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275413232

    APA Style (7th edition)

  • Horvath, Samantha. Spectroscopy and Dynamics of Weakly-bound Anions Using Full- and Reduced-dimensional Theoretical Models. 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1275413232.

    MLA Style (8th edition)

  • Horvath, Samantha. "Spectroscopy and Dynamics of Weakly-bound Anions Using Full- and Reduced-dimensional Theoretical Models." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275413232

    Chicago Manual of Style (17th edition)