SINGLE CRYSTAL ROTATION FOR 250GHZ ESR

250GHZ ESR 的单晶旋转

• 批准号: 7420431
• 负责人: KEITH A EARLE
• 金额: $ 1.13万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7420431
• 关键词: cold temperature; heavy metals; ions; metalloenzyme; model; orientation; relaxation; temperature

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. High-field ESR spectra offer considerable improvements in orientational resolution over low field spectra, in many cases. Recognizing this, we have now successfully extended our capabilities to single-crystal rotation studies of Kramers and non-Kramers transition metal ions at high fields. Our design was influenced by single and multi-axis goniometers at W-band. However, we have incorporated a number of features into our design, which are specifically tailored to facilitate operation at low temperatures in a Fabry-P¿rot resonator. Multifrequency studies of single-crystal rotations allow one to more precisely determine the orientation-dependent terms in the spin-hamiltonian, such as the g-matrix, hyperfine-matrix and the zero-field splitting (ZFS) tensor. At sufficiently high fields, high-field spectra of single crystals with their narrower intrinsic linewidth compared to powder spectra may be used to assign the diagonal ZFS terms with confidence. At lower fields, the off-diagonal terms in the ZFS tensor become significant. This information, along with careful modeling of the ESR active moiety, can be used to obtain important structural information. Single-crystal studies of metalloenzymes with large ZFS splittings will particularly benefit from a multifrequency approach. Given the low or imperfect symmetry of many important biological systems, it is important to develop a goniometer that will work smoothly in a multi-frequency spectrometer with a multi-axis capability, as well as have efficient operation at low-temperatures for systems with short relaxation times. An improved version of the single-axis goniometer we have been using hitherto, featuring higher precision, is nearly completed and will serve as a test bed for developing a high precision multi-axis goniometer. We will incorporate this higher precision goniometer into our newly developed broadband bridge with improved temperature control and higher sensitivity to facilitate the study of a variety of biologically relevant single crystals.

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。在许多情况下，高场ESR谱在取向分辨率上比低场谱有相当大的改进。认识到这一点，我们现在已经成功地扩展了我们的能力，在高场的Kramers和非Kramers过渡金属离子的单晶旋转研究。我们的设计受到W波段单轴和多轴测角仪的影响。然而，我们在设计中融入了许多特性，这些特性是专门为便于在法布里-珀罗谐振器中的低温操作而量身定制的。单晶转动的多频研究使人们能够更精确地确定自旋哈密顿量中与取向相关的项，如g矩阵、超精细矩阵和零场分裂张量。在足够高的电场下，与粉末光谱相比，具有更窄的本征线宽的单晶的高场光谱可以被用于置信地分配对角项。在较低的场，非对角项在张量中变得重要。该信息，沿着ESR活性部分的仔细建模，可用于获得重要的结构信息。多频方法将特别有利于对具有大的电子分裂的金属酶的单晶研究。鉴于许多重要的生物系统的低对称性或不完全对称性，重要的是开发一种测角仪，该测角仪将在具有多轴能力的多频光谱仪中平稳工作，并且对于具有短弛豫时间的系统在低温下具有有效的操作。改进型单轴测角仪已接近完成，它具有更高的精度，可作为研制高精度多轴测角仪的试验台。我们将把这种更高精度的测角仪纳入我们新开发的宽带电桥中，该电桥具有改进的温度控制和更高的灵敏度，以促进各种生物相关单晶的研究。