Spectroscopic Instrumentation

Abstract

This chapter is devoted to a discussion of instruments and techniques that are of fundamental importance for the measurements of wavelengths and line profiles, or for the sensitive detection of radiation. The optimum selection of proper equipment or the application of a new technique is often decisive for the success of an experimental investigation. Since the development of spectroscopic instrumentation has shown great progress in recent years, it is most important for any spectroscopist to be informed about the state-of-the-art regarding sensitivity, spectral resolving power, and signal-to-noise ratios attainable with modern equipment.

At first we discuss the basic properties of spectrographs and monochromators. Although for many experiments in laser spectroscopy these instruments can be replaced by monochromatic tunable lasers (Chap. 5 and Vol. 2, Chap. 1), they are still indispensible for the solution of quite a number of problems in spectroscopy.

Probably the most important instruments in laser spectroscopy are interferometers, which are applicable in various modifications to numerous problems. We therefore treat these devices in somewhat more detail. Recently, new techniques of measuring laser wavelengths with high accuracy have been developed; they are mainly based on interferometric devices. Because of their relevance in laser spectroscopy they will be discussed in a separate section.

Great progress has also been achieved in the field of low-level signal detection. Apart from new photomultipliers with an extended spectral sensivity range and large quantum efficiencies, new detection instruments have been developed such as image intensifiers, infrared detectors, charge-coupled devices (CCDs) or optical multichannel analyzers, which could move from classified military research into the open market. For many spectroscopic applications they prove to be extremely useful.