Measurement of Time Varying Optical Absorption
Measurement of Time Varying Optical Absorption
复制标题
随时间变化的光学吸收的测量
DOI：
10.1063/1.1771237
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发表时间：
1955
期刊：
影响因子：
--
通讯作者：
J. Pack
中科院分区：
文献类型：
--
作者：
A. Phelps;J. Pack
时间采样技术已被应用于光吸收瞬变过程的研究。描述了该方法在研究脉冲放电后亚稳态原子浓度衰减方面的应用。来自毛细管源的光通过放电管。用干涉滤光片和选通光电倍增管测量了被亚稳态原子吸收的其中一条谱线的透射光强。光电倍增管门以两倍的放电频率出现，因此光电倍增管输出的交替脉冲因吸收而减少。在放电频率下输出的光电倍增管的分量与吸收成正比，可以用窄带放大器和同步探测器来测量。由于系统的时间分辨率由光电倍增管门的宽度确定，因此同步探测器的响应可以足够慢，以求在许多衰减周期内对吸收信号进行平均。离开光电倍增管阴极的电子数的波动将本系统的有效灵敏度限制在104的大约两个部分。这代表着灵敏度比以前的技术提高了100倍。给出了氦亚稳态的一些研究结果，以说明用这种技术可以获得的细节。
Time sampling techniques have been applied to the study of optical absorption transients. The method is described in terms of its use for the study of the decay of the concentration of metastable atoms following a pulsed discharge. Light from a capillary source is passed through the discharge tube. The transmitted intensity of one of the spectral lines which is absorbed by the metastable atoms is measured using an interference filter and a gated photomultiplier. The photomultiplier gate occurs at twice the discharge frequency so that alternate pulses of the photomultiplier output are reduced by absorption. The component of the photomultiplier output at the discharge frequency is proportional to the absorption and can be measured with a narrow band amplifier and synchronous detector. Since the time resolution of the system is determined by the width of the photomultiplier gate, the response of the synchronous detector can be made slow enough to average the absorption signal over many decay periods. Fluctuations in the number of electrons leaving the cathode of the photomultiplier limit the useful sensitivity of the present system to approximately two parts in 104. This represents a hundredfold improvement in sensitivity over that available with previous techniques. The results of some studies of helium metastables are presented in order to illustrate the detail which can be obtained with this technique.