title: Observing superradiant decay of excited-state helium atoms inside helium plasma.
abstract: Using femtosecond transient absorption spectroscopy on excited-state helium atoms in a plasma created through optical field ionization, we measured the decay of 2(3)S-2(3)P excitation with sub-ps temporal resolution. The population evolution shows that initial decay is significantly faster than the electron-atom collisions and three orders of magnitude faster than the single atom spontaneous decay rate. This indicates on superradiant coherent behavior of the atomic system inside the plasma.
authors.affiliation: Princeton University, Princeton, New Jersey 08542, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Xia
authors.forename: Anatoly A
authors.initials: AA
authors.lastname: Svidzinsky
authors.forename: Luqi
authors.initials: L
authors.lastname: Yuan
authors.forename: Chao
authors.initials: C
authors.lastname: Lu
authors.forename: Szymon
authors.initials: S
authors.lastname: Suckewer
authors.forename: Marlan O
authors.initials: MO
authors.lastname: Scully