Spectroscopic decay-rate measurements below the laser linewidth

Abstract

When two levels can be strongly coupled by a pulsed laser, it is possible to measure the decay rate from the upper state by applying sufficient laser power to depletion broaden the transition. The depletion broadening is proportional to the square root of the decay rate times the total energy density of the laser pulse. With sufficient laser power, this technique can be used even if the decay rate is smaller than inhomogeneous broadenings or the laser linewidth. The technique is used here to measure autoionizing rates of some 6P((1/2))ns states.