Department of Physics, East Carolina University, Howell Science Complex, E. 10th Street, Greenville, North Carolina 27858-4353, USA.
Appl Spectrosc. 2012 Feb;66(2):180-7. doi: 10.1366/11-06417.
Circular dichroism (CD), defined as the difference in absorption between left and right circularly polarized light, is used to spectroscopically study the structures of chiral materials. In this article, various methodologies are presented for characterizing the performance of CD spectrometers to determine (1) experimental conditions for optimal data collection, (2) noise characteristics dependent on machine parameters, (3) the relative significance of spectral data as a function of detector gain, and (4) stray light and dark current as a function of wavelength. The results of case studies of two commercial CD spectrometers (specifically, Jasco J810 and J815) are described. The analyses show that the variation of CD signal is Poisson distributed and hence can be considered shot noise. Also, optimum scan parameters are established and a weighting function of CD data significance is produced so that wavelength-dependent gain (as determined by the high tension, HT, voltage applied to the photomultiplier tube, PMT, detector) can be accommodated. Lastly, the amount of stray light and dark current for the photomultiplier tube is determined. Though specific to the Jasco CD spectrometers characterized in this study, it is expected that all CD spectrometers exhibit similar behavior and the methodology described here can be usefully applied to characterize CD spectrometers independent of manufacturer.
圆二色性（CD），定义为左、右旋圆偏振光之间的吸收差异，用于光谱学研究手性材料的结构。本文提出了各种方法来表征 CD 光谱仪的性能，以确定（1）最佳数据采集的实验条件，（2）依赖于机器参数的噪声特性，（3）作为探测器增益函数的光谱数据的相对重要性，以及（4）作为波长函数的杂散光和暗电流。描述了两个商用 CD 光谱仪（具体为 Jasco J810 和 J815）的案例研究结果。分析表明，CD 信号的变化呈泊松分布，因此可以认为是散粒噪声。此外，建立了最佳扫描参数，并产生了 CD 数据重要性的加权函数，以便适应（由施加到光电倍增管（PMT）探测器的高压（HT）电压确定的）波长相关增益。最后，确定了光电倍增管的杂散光和暗电流的量。尽管特定于本研究中所描述的 Jasco CD 光谱仪，但预计所有 CD 光谱仪都表现出类似的行为，并且此处描述的方法可用于表征独立于制造商的 CD 光谱仪。
