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横向弛豫时间T₂与自旋中心浓度关系的脉冲EPR研究

Study on the Relationship between Concentration and Transverse Relaxation Time T₂ of Spin Center by Pulsed EPR

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【Author】 BI Weili;LIU Yanhong;SHI Zhifu;SANG Yuanbo;LI Yong;YANG Haijun;Institute of Tibetan Plateau Research, Chinese Academy of Sciences;Technical Institute of Physics and Chemistry, CAS;Chinainstru & Quantumtech (Hefei) Co., Ltd.;Analysis Center, Tsinghua University;

【机构】中国科学院青藏高原研究所；中国科学院理化技术研究所；国仪量子(合肥)技术有限公司；清华大学分析中心；

【摘要】 <正>长期以来,电子顺磁共振波谱在自旋中心定量方面的研究困难重重。主要原因在于影响定量测定结果的因素众多,比如测试条件、标准品的选择、仪器参数和操作规范性等。目前通常所采用半定量的测定方法,即用连续波实验中得到的顺磁共振信号强度或者二次积分面积定量计算自旋中心的浓度,这种单一的定量测量方式得不到校正与比对,无法排除或衡量仪器、操作或标准样品等因素对定量结果的影响程度。国仪量子公司生产的X波段脉冲式电子顺磁共振谱仪(EPR100)提供了脉冲实验的平台。更多还原

【Abstract】 Quantitative electron paramagnetic resonance（EPR） study has always been a challenging task. The reason is that, numerous factors could essentially affect the precision of quantification, including the measurement conditions, the choice of reference samples, the settings of parameters and the reliability of laboratory operations. The majority of the standard methods are in fact semi-quantitative, calculating the concentration of paramagnetic centers based on the intensity or integral of the signal obtained from continuous wave experiments. Without proper normalization or correction, it is difficult to judge the degree of influence, for example from the experimental conditions, the operations or the quality of standard samples. To this end, a Chinese company, CIQTEK, have developed an X-band pulsed EPR spectrometer（EPR100）, which offers a new opportunity and meanwhile provides an advanced platform for quantitative EPR studies in China. With the help of the EPR100, in this work the transverse relaxation times T₂ were measured and the correlation between T₂ and concentrations of paramagnetic centers was successfully obtained. The study was made with a sample compound, free radical TEMPO, at 100 K. The results showed that the T₂ is inversely proportional to the concentration of TEMPO within error limits, which provides a quantification prototype and in addition, sheds light on future quantitative EPR studies especially in China. The outlook for the following research relates to further tests on different model compounds, as the T₂ relaxation behavior of paramagnetic species is known to be sample-type dependent.更多还原