Atomic level crossings in laser excitation

The underlying principle of the level crossing method is reviewed, and level crossing signal shapes, lag detection in level crossings, level crossings in atomic states populated by stepwise optical excitation, and level crossings in Rybderg states with cascaded fluorescence are discussed. Wideband excitations, excitation of atoms at rest by monochromatic radiation, excitation of atoms in a mixture using radiation of specified spectral distribution, and tunable laser applications are discussed. Excitation by electron impact, RF spectroscopy and level crossing spectroscopy, and conditions under which excitation using an overmoded laser is feasible, are dealt with.