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On Phase and the \uD835\uDF12(3) Effect in Second-Order Nonlinear Spectroscopy
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | On Phase and the \uD835\uDF12(3) Effect in Second-Order Nonlinear Spectroscopy. |
| 개인저자 | Ohno, Paul Erich. |
| 단체저자명 | Northwestern University. Chemistry. |
| 발행사항 | [S.l.]: Northwestern University., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 140 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-05B. Dissertation Abstract International |
| ISBN | 9781088328347 |
| 학위논문주기 | Thesis (Ph.D.)--Northwestern University, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-05, Section: B.
Advisor: Geiger, Franz. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | The physical boundary layer, or interface, between two different phases of matter is the site of chemical and physical processes that are critical to many research fields. Many of these interfaces contain electric charge, which influences the structure and composition of the interfacial region and the interactions between the interface and chemical species. Thus, the development of experimental techniques capable of probing surface charge, interfacial potential, and the structure of the electrical double layer (EDL) is crucial to solving outstanding questions in research areas spanning physical chemistry, the life sciences, geochemistry, and beyond. In this thesis, we detail efforts to rigorously understand the effects of surface charge on the signal generation process of two common interfacial spectroscopies, second harmonic generation (SHG) and sum frequency generation (SFG), with a particular emphasis on the optical phase of the generated signal. We report nonresonant SHG measurements of the 慣-quartz/water interface that show optical interference that cannot be explained by the standard mathematical framework that has been used to interpret SHG data from charged interfaces for more than two decades. The observed optical interference is, however, predicted by a recently proposed framework that takes into account optical interference throughout the diffuse layer of the EDL, and these SHG measurements provide the first direct experimental evidence for this updated framework.We also report the design and construction of a new heterodyne-detected SHG instrument capable of measuring not only the intensity of the signal produced at a charged interface, but also its phase. We show how this additional phase information can be used to separate the signal into two different terms. The first term is generated near the boundary plane and can be used to track the structure, composition, and dynamics in this region. The second term is proportional to the interfacial potential, allowing SHG to be used as an "optical voltmeter". We comment on the possibilities for the instrument presented here to, in an all optical and label-free manner, quantify absolutely the interfacial potential, determine the exact point of charge reversal at interfaces, and measure the Debye screening length.Finally, we detail the implications of this updated mathematical framework on the SFG spectra of charged interfaces. We use mathematical modeling to show that different contributions to the overall SFG spectra may mix in previously unforeseen ways. Because of this mixing, we present a way to correct newly acquired spectra for the previously overlooked interactions so that molecular structure at interfaces can be accurately deduced. We also include a detailed analysis of one of the most well-studied interfaces, the air/water interface, using computed SFG spectra derived from MD simulations. |
| 일반주제명 | Chemistry. Physical chemistry. |
| 언어 | 영어 |
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