Suppression and enhancement of transition rates

Since the 17d state is bound by 380 cm 1, which exceeds kT, the photoionization rate varies rapidly with temperature, roughly a factor of 100 between 90 K and 300 K, as shown by Fig. 5.7. The rapid, nearly exponential, dependence of the photoionization rate on temperature shown in Fig. 5.7 is to be contrasted with the linear temperature dependence of the 19s — 19p, 18p transfer rate shown in Fig. 5.6. 

We have described the effects of black body radiation in free space. In a closed cavity the radiation is confined to the allowed modes of the cavity. In essence all the thermal radiation is forced into the cavity modes, raising the intensity at the 

In the experiment Na atoms are excited by two lasers from the ground state to the nd state in an environment cooled to 180 K at which point n = 86 for the 29d — 30p transition. The atoms are exposed to the thermal radiation for 20 / , 

In any low angular momentum state the radiative decay rate is usually dominated by the high frequency transitions to low lying states, and as a result it is impossible to control completely the decay rate using a millimeter wave cavity. In a circular i = m = n - 1 state the only decay is the far infrared transition to the n — 1 level, and Hulet et al. have observed the suppression of the decay of this level.26 They produced a beam of Cs atoms in the circular n = 22, = m = 21 state by pulsed laser excitation and an adiabatic rapid passage technique.27 The beam of circular state atoms then passed between a pair of plates 6.4 cm wide, 12.7 cm long, spaced by 230.1 jum, and held at 6 K. The 0 K radiative lifetime is 460ps, and 

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