Problems in laser spectroscopy
Institute of Spectroscopy, Russian Academy of Sciences, ul. Fizicheskaya 5, Troitsk, Moscow, 108840, Russian Federation
The introductory section of the review lists the main problems which can be solved by laser spectroscopy methods: 1) achievement of the ultimate resolving power; 2) suppression of the Doppler broadening in the gaseous phase; 3) attainment of the ultimate sensitivity in spectroscopic analysis of atoms and molecules; 4) investigation of the spectra and relaxation originating from excited states; 5) remote spectroscopic analysis; 6) local spectroscopic analysis. This is followed by a section which presents the current status of tunable lasers, including dye solution, semiconductor, and high-pressure molecular gas lasers, parametric oscillators, and spin-flip lasers; nonlinear frequency conversion methods are also considered. Next, a more detailed analysis is made of the following types of laser spectroscopy: 1) linear spectroscopy (external absorption, intraresonator absorption, optoacoustic, and fluorescence methods, and a comparison of these methods); 2) nonlinear spectroscopy free of the Doppler broadening (absorption saturation, two-photon, and particle ``trapping'' method; a comparison of the sensitivity and resolution of these methods; new spectroscopic information; precision spectroscopy); 3) Raman (spontaneous, inverse, and active) spectroscopy; 4) two-photon absorption spectroscopy; 5) selective detection of small amounts of atoms and molecules (local and remote detection); spectroscopy of excited states, high states of atoms, and vibrattonal states of molecules; picosecond laser spectroscopy of excited molecules).