Intracavity Laser Absorption Spectroscopy
نویسندگان
چکیده
continued on page 4 continued on page 4 Theodor Hänsch makes a time measurement. Introduction Absorption spectroscopy is one of the oldest scientific methods for studying atomic and molecular structure. It is also one of the most powerful research tools for providing information about the world around us. One important application is ultrasensitive trace gas analysis, which is used in many areas from environmental monitoring to high technology applications. Absorption spectroscopy is based on the Lambert-Beer law. Many methods of sensitive detection of absorption exist. This article will review several of these and focus on a new one, Intracavity Laser Absorption Spectroscopy (ICLAS). The physical limit to the minimum detectable concentration for a given absorption path length is determined by the shot noise of the detected photons. There are two ways to increase the sensitivity of an absorption measurement: increasing the absorption path length, or decreasing the noise. The first method, which can be used with both classical and laser sources, employs a mirror system which produces multiple passes of light in a limited cell volume (multi-pass cell, or MPC). One of the best known MPC’s was introduced by White in 1942, and an improved version is still widely used today. Many other more or less sophisticated MPC designs have been introduced since then. This approach Theodore Hänsch Selected as Eighth Lord Lecturer
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تاریخ انتشار 1999