95GHZ HIGH POWER PULSE ESR SPECTROMETER

这个子项目是利用资源的许多研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 子项目的主要研究者可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 在95 GHz和更高的脉冲技术已经被技术限制在最近的过去，以50 ns和更长的带宽有限的脉冲。 虽然这些选择性脉冲可用于在固态下进行各种低温实验，但由于这些系统的特征是快速弛豫，因此它们不适合于在生理温度下研究流体系统中的动力学。 因此，我们已经建立了一个新的，高功率，脉冲95 GHz光谱仪的基础上，1千瓦的扩展相互作用速调管放大器，克服了传统的95 GHz脉冲光谱仪的局限性。光谱仪使用专用的6 T磁体，使其能够独立操作。我们已经实现了迄今为止的π脉冲的5 ns，全相位循环能力的抑制不必要的相干，150 MHz的覆盖范围和死区时间的30 ns在有利的情况下。 在HFHF-ESR的背景下执行2D-FT-ESR实验的能力可能是非常有用的，特别是由于与常规频率下的ESR相比，对动态细节的灵敏度增强。 这对于研究脂质膜的动态结构特别重要。 在常规ESR频率下，由于常规ESR的较低取向分辨率，排序张量的细节是模糊的。 我们已经成功地进行了各种水溶液样品和定向脂膜样品的时域实验，以利用我们的光谱仪在这些异质系统中的动态结构的分辨率增强。 一种新型法布里-珀罗谐振器的内部开发与连续可变耦合是这些实验成功的关键。 我们目前正在扩展我们的研究，以面向脂膜深在慢运动制度。 虽然我们的短脉冲的目前可用的光谱覆盖范围是不是最佳的探索所有的细节的动态，然而，我们已经成功地记录了2D-ELDOR光谱的光谱范围约为500 MHz。 我们还对计时系统进行了实质性的改进，这些改进已经接近完成，这对于我们最初的慢动作2D-ELDOR实验的成功至关重要。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Pulse techniques at 95GHz and higher have been constrained by technical limitations in the recent past to bandwidth limited pulses of 50ns and longer. While these selective pulses are useful for performing a variety of low temperature experiments in the solid state, they are not suitable for studying dynamics in fluid systems at physiological temperatures, due to the rapid relaxation that characterizes these systems. We have, therefore, built a new, high-power, pulsed 95GHz spectrometer based on a 1kW extended interaction klystron amplifier that overcomes the limitations of conventional 95GHz pulsed spectrometers. The spectrometer uses a dedicated 6T magnet allowing it to be operated independently. We have achieved to date pi pulses of 5ns, full phase cycling capability for the suppression of unwanted coherences, 150MHz coverage and dead times of 30ns in favorable cases. The ability to perform 2D-FT-ESR experiments within the context of HFHF-ESR can be extremely useful, particularly due to the demonstrated enhanced sensitivity to details of dynamics compared to ESR at conventional frequencies. This is particularly important for studying the dynamic structure of lipid membranes. At conventional ESR frequencies, the details of the ordering tensors are ambiguous due to the lower orientational resolution of conventional ESR. We have successfully performed a variety of time-domain experiments on aqueous samples and oriented lipid membrane samples in order to exploit the enhanced resolution of our spectrometer to dynamic structure in these heterogeneous systems. The in-house development of a novel Fabry-P¿rot resonator with continuously variable coupling was crucial for the success of these experiments. We are currently extending our studies to oriented lipid membranes deep in the slow-motional regime. Although the currently available spectral coverage of our short pulses is not optimum for exploring all of the details of the dynamics, nevertheless, we have successfully recorded 2D-ELDOR spectra with a spectral extent of approximately 500MHz. We are also making substantial improvements to the timing system that are nearly complete and which will be crucial for building on the success of our initial slow-motional 2D-ELDOR experiments.