MEASURING FAST ELECTRON SPIN RELAXATION

描述（改编自申请人摘要）：电子顺磁 共振（EPR）光谱用于表征过渡金属， 有机自由基，以及金属之间或金属之间的相互作用， 有机自由基，在生物系统中。 EPR的定量应用 这些研究的技术需要顺磁性的T（1）的知识 物种 脉冲EPR和连续波（CW）EPR提供了测量非常 长的和非常短的弛豫时间，但在 至少有两个数量级的弛豫时间重叠， 具有重要生物学意义的金属。 建议构建一个附件， EPR光谱仪，并开发实施方法的方法 基于微波幅度调制， 固体物理实验 将提供订单的增强功能 灵敏度提高了一个数量级， 测量较短弛豫时间能力相对于现有技术的改进 这些努力包括使用创新的交叉环（双峰）谐振器 (CLR)，200 MHz锁定放大器，最近已成为商业 提供，并使用双平衡混频器（DBM）提供 微波振幅的高速调制。 调制 光谱系统将作为商业EPR的附件 光谱仪 T（1）将使用调制光谱测量， 已通过脉冲法测量了长T（1）值和短T（1）值的样品 和CW方法，以测试值是否在长和短重叠 预期调制光谱的范围的末端 重要.

DESCRIPTION (Adapted from the applicant's abstract): Electron paramagnetic resonance (EPR) spectra are used to characterize transition metals and organic radicals, and interactions among metals or between metals and organic radicals, in biological systems. Quantitative application of EPR techniques for these studies requires knowledge of T(1) of the paramagnetic species. Pulsed EPR and continuous wave (CW) EPR provide measures of very long and very short relaxation times, but there is a "blind" region of at least two orders of magnitude that overlaps the relaxation times of many metals of biological importance. It is proposed to construct an accessory to an EPR spectrometer and develop the methodology to implement a method based on microwave amplitude modulation, which builds upon background experiments in solid state physics. Enhancements that will provide an order of magnitude improvement in sensitivity and about an order of magnitude improvement in ability to measure shorter relaxation time relative to prior efforts include the use of an innovative crossed-loop (bimodal) resonator (CLR), a 200 MHz lock-in amplifier that has recently become commercially available, and the use of a double-balanced mixer (DBM) to provide high-speed modulation of the microwave amplitude. The modulation spectroscopy system will be built as an accessory for a commercial EPR spectrometer. T(1) will be measured with modulation spectroscopy using samples for which long and short T(1) values have been measured by pulsed and CW methods, to test whether the values overlap at the long and short ends of the range for which modulation spectroscopy is expected to be important.