SENSITIVITY ENHANCEMENT IN FIELD-MODULATED CW ENDOR VIA RF BANDWIDTH BROADENING
SENSITIVITY ENHANCEMENT IN FIELD-MODULATED CW ENDOR VIA RF BANDWIDTH BROADENING
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DOI：
10.1006/jmra.1994.1180
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发表时间：
1994-09-01
期刊：
影响因子：
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通讯作者：
DAVOUST, CE
中科院分区：
文献类型：
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作者：
HOFFMAN, BM;DEROSE, VJ;DAVOUST, CE
在低温ENDOR研究中，通常在nu（mod）类似于100 kHz处调制磁场，并观察ENDOR响应作为在nu（mod）处解码的色散模式快速通过EPR信号的变化。通过将RF载波信号与可变带宽的白噪声源混合，非相干地加宽所施加的RF的带宽，可以增加该过程的灵敏度。通过监测ENDOR信号的幅度和宽度作为RF带宽和功率的函数，在Fe-57信号来自金属蛋白和N-14，H-1信号来自两种Cu（II）化合物的情况下，已经探索了这种技术。RF频带加宽产生了超过三倍的信号增强。结果解释为（i）在非均匀加宽的ENDOR线内激发的自旋包数的增加和（）每个包的响应的减少之间的竞争。简单的分析导致ENDOR响应随入射RF功率和带宽的变化的方程，其分别由饱和RF功率和有效自旋包宽度缩放。(C)1994年出版社出版。
In low-temperature ENDOR studies it is common to modulate the magnetic field at nu(mod) similar to 100 kHz and to observe the ENDOR response as a change in the dispersion-mode rapid-passage EPR signal as decoded at nu(mod). The sensitivity of this procedure can be increased by incoherently broadening the bandwidth of the applied RF through mixing of the RF carrier signal with a white-noise source of variable bandwidth. This technique has been explored by monitoring the amplitude and width of ENDOR signals as a function of the RF bandwidth and power, in the case of the Fe-57 signals from a metalloprotein and N-14, H-1 signals from two Cu(II) compounds. The RF band broadening has produced signal enhancements of over threefold. The results are interpreted in terms of a competition between (i) an increase in the number of spin packets excited within the inhomogeneously broadened ENDOR line and () a reduction in the response per packet. Simple analysis leads to equations for the variation in the ENDOR response with incident RF power and bandwidth that are scaled by a saturation RF power and an effective spin-packet width, respectively. (C) 1994 Academic Press, Inc.