CIRCULAR DICHROISM ESR

圆二色性 ESR

• 批准号: 7956584
• 负责人: KEITH A EARLE
• 金额: $ 0.4万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7956584
• 关键词: Affect; Biology; Chemistry; Circular Dichroism; Code; Computer Retrieval of Information on Scientific Projects Database; Electron Spin Resonance Spectroscopy; Frequencies; Funding; Grant; Heating; Institution; Morphologic artifacts; Optics; Research; Research Personnel; Resources; Sampling; Signal Transduction; Source; Techniques; Technology; Testing; United States National Institutes of Health; absorption; flexibility; magnetic field; prevent

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. One of the important issues that affects the applicability of ESR spectroscopy to a wide range of problems in chemistry and biology is the constraint of magnetic field modulation on the S/N. In order to maximize the signal, one needs modulation amplitudes that are comparable to the linewidth. For high-field/high-frequency-ESR (HFHF-ESR), Lorentz forces limit field modulation amplitudes to less than 20G in order to prevent excessive sample heating. However, many HFHF-ESR linewidths are often greater than 100G, and so it is desirable to develop alternatives to field modulation. In general, some form of signal coding is usually necessary to have an observable signal. We are currently exploring the possibility of using techniques that are common in optical circular dichroism (CD) spectropolarimeters and adapting them to a HFHF-ESR spectrometer to modulate the ESR resonance without using magnetic field modulation. We call the technique CD-ESR. The technique relies on illuminating the ESR sample with two oppositely circularly polarized beams in alternation at a given reference frequency. There is preferential absorption within the ESR sample of one of the circular polarization states which satisfies the so-called Transfer of Modulation principle. Recent efforts have focused on developing a polarization modulator with equal amplitudes of both circular polarization states in order to minimize instrumental artifacts. The recent upgrades that we have made to our HFHF ESR spectrometers will facilitate the implementation of this technique. We are also currently investigating the possibility that our cw sources at 170 and 240GHz may be modified to provide a rugged, reliable means for achieving the necessary polarization modulation. The modified reflection bridge we are implementing is sufficiently flexible to allow for us to test these ideas in a straightforward way.

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