ABSTRACT
A broad class of problems, ranging from the fundamental to the practical, critically depends on the ability to measure atomic and molecular spectra with high precision. At first glance, tunable continuous-wave lasers, characterized by high spectral purity and variable frequency output, appear both sufficient and ideal for probing the finest spectral features of atomic and molecular transitions. However, motions of the atoms or molecules relative to the laser undermine the nearly perfect features of the laser as a spectroscopic tool. Because of the Doppler effect, narrow resonance peaks can become significantly broadened. This entry provides an overview of the powerful techniques for circumventing the detrimental effects of Doppler broadening.
