STEP-SCAN FOURIER-TRANSFORM INFRARED SPECTROMETER
STEP-SCAN FOURIER-TRANSFORM INFRARED SPECTROMETER
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DOI：
10.1063/1.1142003
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发表时间：
1991-05-01
影响因子：
1.6
通讯作者：
CHAO, JL
中科院分区：
文献类型：
--
作者：
MANNING, CJ;PALMER, RA;CHAO, JL
本文介绍了用于步进扫描操作的商用傅里叶变换红外光谱仪的改进。步进扫描操作将FT-IR光谱复用与时间解耦，因此适用于各种时间相关的光谱实验，特别是光声和光热光谱。所描述的步进扫描仪器用反馈回路控制延迟（移动镜位置）。环路使用路径差，或相位，调制参考激光强度，与锁相放大器一起检测镜子的位置。由于干涉图的采样间隔可小至1/4 λ - hene，因此最大自由光谱范围为31 600 cm-1。对于镜子的初始定位，步进可以快到100赫兹。目前的软件将允许以大约1.6 Hz的频率收集数据，尽管小于或等于20 ms的镜像沉降时间将允许使用更高效的软件以20-30 Hz的步进频率收集数据。镜面控制相位调制（PM）也可以用于红外光束的有效调制，利用1-2- λ - hene数量级的PM振幅。延迟的稳定性约为+/- 15 nm，这对测量光谱的信噪比施加了上限。对于8 cm-1分辨率，典型的数据收集时间为20分钟。给出了采用步进扫描方式获得动态光谱数据的实例。简要讨论了该仪器今后的改进。
This article describes the modification of a commercial Fourier-transform infrared (FT-IR) spectrometer for step-scan operation. Step-scan operation decouples the FT-IR spectral multiplexing from time and is therefore applicable to a variety of time-dependent spectroscopic experiments, including, particularly, photoacoustic and photothermal spectroscopy. The step-scan instrument described controls the retardation (moving mirror position) with a feedback loop. The loop uses path difference, or phase, modulation of the reference laser intensity, together with lock-in amplifiers to detect the mirror position. Since the interferogram can be sampled at intervals as small as 1/4-lambda-HeNe, the maximum free-spectral range is 31 600 cm-1. For initial positioning of the mirror, stepping can be as rapid as 100 Hz. The current software will allow data collection at approximately 1.6 Hz, although the mirror settling time of less-than-or-equal-to 20 ms would allow data to be collected at 20-30 Hz stepping frequency with more efficient software. The mirror control phase modulation (PM) can also be used for efficient modulation of the infrared beam by use of a PM amplitude on the order of 1-2-lambda-HeNe. The stability of the retardation, which imposes an upper limit on the SNR of the measured spectra, is approximately +/- 15 nm. Data collection times on the order of 20 min are typical for 8 cm-1 resolution. Examples of dynamic spectroscopic data obtained using the step-scan mode of operation are presented. Future improvements to the instrument are briefly discussed.