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。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 在最近的过去，95 GHz和更高频率的脉冲技术受到技术限制，仅限于50 ns或更长的带宽脉冲。虽然这些选择性脉冲对于在固体中执行各种低温实验是有用的，但它们不适合于在生理温度下研究流体系统中的动力学，因为这些系统具有快速松弛的特点。因此，我们建立了一台基于1kW扩展互作用速调管放大器的新型高功率脉冲95 GHz光谱仪，克服了传统95 GHz脉冲光谱仪的局限性。光谱仪使用专用的6T磁铁，使其能够独立操作。到目前为止，我们已经实现了5 ns的pi脉冲，抑制不需要的相干的全相位循环能力，150 MHz覆盖，在有利的情况下死区时间为30 ns。在HFHF-ESR的背景下进行2D-FT-ESR实验的能力可能非常有用，特别是由于与传统频率下的ESR相比，对动力学细节的敏感性得到了增强。这对于研究脂膜的动态结构尤为重要。在常规ESR频率下，由于常规ESR的取向分辨率较低，有序张量的细节是模糊的。我们已经成功地对水样和定向脂膜样品进行了各种时间域实验，以开发我们的光谱仪对这些非均相体系中动态结构的增强分辨率。对于这些实验的成功，内部开发了一种新型的具有连续可变耦合的法布里-P？罗谐振器。我们目前正在将我们的研究扩展到缓慢运动状态下的定向脂膜。虽然我们目前可用的短脉冲的光谱覆盖范围对于探索动力学的所有细节并不是最佳的，然而，我们已经成功地记录了频谱范围约为500 MHz的2D-Eldor光谱。我们还对即将完成的计时系统进行了实质性的改进，这将是我们最初缓慢运动的2D-Eldor实验取得成功的关键。

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.