Modulated emission in iodine vapor

Abstract

The response of emission in I2 vapor to intensity modulated light at radial frequency ω is measured and described in terms of the lifetime of the excited state, T1, the rate of phase interrupting collisions γ, and the inhomogeneously broadened absorption line. When the laser is tuned to resonance, the variation of amplitude of the modulated emission with ω corresponds to a single exponential decay with lifetime T1. Off resonance, the modulation is described as the sum of the above ‘‘delayed’’ component and a ‘‘prompt’’ in‐phase component which is independent of modulation frequency. The ratio of the delayed to prompt component for off resonant excitation is shown to be 2γT1. This relation is used to determine the rate of phase interrupting collisions in I2 vapor.