McPeak Joseph E, Quine Richard W, Eaton Sandra S, Eaton Gareth R
Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80210, USA.
Ritchie School of Engineering and Computer Science, University of Denver, Denver, Colorado 80210, USA.
Rev Sci Instrum. 2019 Feb;90(2):024102. doi: 10.1063/1.5043316.
An X-band (ca. 9-10 GHz) continuous wave saturation recovery spectrometer to measure electron spin-lattice relaxation (T) was designed around an arbitrary waveform generator (AWG). The AWG is the microwave source and is used for timing of microwave pulses, generation of control signals, and digitizer triggering. Use of the AWG substantially simplifies the hardware in the bridge relative to that in conventional spectrometers and decreases the footprint. The bridge includes selectable paths with different power amplifications to permit experiments requiring hundreds of milliwatts to fractions of nanowatts for the pump and observe periods. The signal is detected with either a single or quadrature-output double balanced mixer. The system can operate with reflection or crossed-loop resonators. The source noise from the AWG was decreased by addition of a Wenzel high-stability clock. The source is sufficiently stable that automatic frequency control is not needed. The spectrometer was tested with samples that contained 1 × 10 to 8 × 10 spins and have T between a few hundred ns and hundreds of μs. Excellent signal-to-noise ratio was obtained with acquisition times of 2-90 s. Signal-to-noise performance is similar to that of a conventional saturation recovery spectrometer with a solid-state source. The stability and data reproducibility are better than with conventional sources. With replacement of frequency-sensitive components, this spectrometer can be used to perform saturation recovery measurements at any frequency within the range of the AWG.
围绕任意波形发生器（AWG）设计了一种用于测量电子自旋 - 晶格弛豫时间（T1）的X波段（约9 - 10 GHz）连续波饱和恢复光谱仪。该AWG是微波源，用于微波脉冲定时、控制信号生成以及数字化仪触发。与传统光谱仪相比，使用AWG极大地简化了桥路中的硬件并减小了占地面积。桥路包括具有不同功率放大倍数的可选路径，以允许在泵浦和观测期间进行从数百毫瓦到纳瓦级别的实验。信号通过单输出或正交输出双平衡混频器进行检测。该系统可与反射式或交叉环谐振器配合使用。通过添加Wenzel高稳定性时钟降低了AWG的源噪声。该源足够稳定，无需自动频率控制。使用含有1×10至8×10个自旋且T1在几百纳秒到数百微秒之间的样品对该光谱仪进行了测试。在2 - 90秒的采集时间内获得了出色的信噪比。信噪比性能与具有固态源的传统饱和恢复光谱仪相似。稳定性和数据重现性优于传统源。通过更换频率敏感组件，该光谱仪可用于在AWG范围内的任何频率下进行饱和恢复测量。
