THE DYNAMICS OF EXCITON TUNNELING AND TRAPPING IN CONDENSED XENON ON ULTRAFAST TIME SCALES

We report the use of picosecond transient absorption spectroscopy to directly observe the dynamics of formation, tunneling, and subsequent cooling of the n = 1, GAMMA(3/2) exciton in condensed xenon over a density range of 0.10 to 1.8 g/ml. At lower densities, only Xe2* excimers are formed, which undergo vibrational cooling on a tens of picoseconds time scale. At densities high enough to support exciton formation, tunneling from the free to the trapped exciton state takes place in less-than-or-equal-to 3 ps, and cooling of the localized exciton takes place in 5-10 ps; neither rate is strongly dependent on Xe density over the range investigated. The results are compared to theories that describe the formation and cooling rates of the trapped exciton state, and are consistent with a resonant energy transfer mechanism in which the excitation hops between neighboring Xe atoms during the trapping process.