Capital Award for Core Equipment 2022/23, National Research Facility for Electron Paramagnetic Resonance Spectroscopy

电子顺磁共振（EPR）光谱，也称为电子自旋共振（ESR），可能是表征顺磁性材料（即包含未成对电子）最强大的技术。未配对电子引起材料的磁性和电子特性，并且在存在时经常控制反应性，因此了解它们的环境和行为是很重要的。从生物过程到磁性材料，顺磁体无处不在；因此，EPR是物理、化学、材料和生物科学中必不可少的工具。EPSRC资助EPR的国家研究设施（NRF），位于曼彻斯特大学（UoM）的光子科学研究所（PSI），为英国学术界提供最先进的实验技术和专业知识。粗略地说，有两种方法进行EPR谱分析：连续波（cw） EPR和脉冲EPR，它们提供互补的信息。脉冲EPR是一种分辨率高得多的技术（允许测量涉及未配对电子的弱得多的相互作用），也可以获得时间分辨的信息。然而，这样的实验可能需要非常低的温度（<10 K），否则信号响应可能不存在或数据收集非常缓慢，需要长时间的数据收集才能获得可接受的信噪比（例如，由于低顺磁体浓度）。对单个样品进行连续测量一周的实验是很常见的。因此，EPR NRF目前运行的三个脉冲EPR光谱仪是迄今为止最超额订购的仪器。其中两个光谱仪有冷却系统，可以提供约2 K的基本温度，可以远程监控和控制，但第三个只能达到10 K，需要手动控制。与即将到来的升级相结合，所有脉冲EPR频率将具有相同的样品温度控制，从而最大限度地提高四个频段（每个光谱仪平台两个）的灵活性和吞吐量：X-/Q-， Q-/S-和X-/ l -波段，注意Q-和X波段是用户社区最需要的频率。对EPR光谱监测的光激发样品的兴趣和使用已经大大增加，这主要是由脉冲或瞬态EPR方法提供服务。像许多脉冲实验一样，数据收集可能很慢，并且将脉冲光激发纳入微波（有时是射频）脉冲序列进一步延长了测量时间。安装一个快速、高功率、可调谐的激光器将提高这些光学实验的容量和效率。结合我们的慢速，低功率可调激光器，EPR光谱仪将能够提供“双色”实验，对此也有越来越多的兴趣。冷却和光激发能力的扩展将增加英国NRF所有用户（包括ecr和博士生）的脉冲EPR容量，新功能将扩大用户群。联系国家EPR设施和服务，请发送电子邮件：epr@manchester.ac.uk和网站：https://www.chemistry.manchester.ac.uk/epr/

Electron Paramagnetic Resonance (EPR) spectroscopy, also known as Electron Spin Resonance (ESR), is possibly the most powerful technique for characterisation of paramagnetic materials, i.e. that contain unpaired electrons. Unpaired electrons give rise to the magnetic and electronic properties of materials and often govern reactivity when present, hence understanding their environment and behaviour is important. Paramagnets are ubiquitous from biological processes to magnetic materials; hence EPR is an essential tool in physics, chemistry, materials and biological sciences. The EPSRC funds a National Research Facility (NRF) for EPR, located in the Photon Science Institute (PSI) at The University of Manchester (UoM), providing access to state-of-the art experimental techniques and expertise for the UK academic community. Crudely, there are two ways to do EPR spectroscopy: continuous wave (cw) EPR and pulsed EPR, which give complementary information. Pulsed EPR is a much higher resolution technique (allowing measurement of much weaker interactions involving the unpaired electron) and also gives access to time-resolved information. However, such experiments can require access to very low temperatures (<10 K) otherwise signal response may be non-existent or data collection very slow, requiring long data collection to get acceptable signal-to-noise (e.g. due to low paramagnet concentration). It is common for an experiment on a single sample to last a week of continuous measurement. As a consequence, the three pulsed EPR spectrometers that the EPR NRF currently runs are by far and away the most oversubscribed pieces of instrumentation. Two of those spectrometers have cooling systems that give base temperature of ca. 2 K and can be remotely monitored and controlled, but the third only reaches 10 K and requires manual control. Allied to a forthcoming upgrade, all pulsed EPR frequencies will have the same sample temperature control, thereby maximising flexibility and throughput across four frequency bands (two per spectrometer platform): X-/Q-, Q-/S- and X-/L-bands, noting that Q- and X-band are most requested frequencies by the user community. There has been a large increase in the interest in and use of optically excited samples monitored by EPR spectroscopy, which are primarily serviced by either pulsed or transient EPR methods. Like many pulsed experiments, data collection can be slow, and the inclusion of pulsed light excitation into the microwave (and sometimes radiofrequency) pulse sequences lengthens measurement time further. Installing a fast, high power, tunable laser will increase capacity and efficiency of these optical experiments. In conjunction with our slower, lower power tunable laser, the EPR spectrometers will be able to deliver 'two colour' experiments, for which there is also growing interest.The extension to cooling and optical excitation capability will increase the capacity for pulsed EPR for all users of the NRF across the UK, including ECRs and doctoral students, and the new capabilities will widen the user base. To contact the National EPR Facility and Service, please email: epr@manchester.ac.uk and web-site: https://www.chemistry.manchester.ac.uk/epr/