title: Enhancement of Rb fine-structure transfer in 4He due to three-body collisions.
abstract: Using ultrafast laser excitation and time-correlated single-photon counting techniques, we have measured the collisional mixing rates between the rubidium 5(2)P fine-structure levels in the presence of (4)He gas. A nonlinear dependence of the mixing rate with (4)He density is observed. We find Rb fine-structure transfer is primarily due to binary collisions at (4)He densities of < or = 10(19) cm(-3), while at greater densities, three-body collisions become significant. We determine a three-body collisional transfer rate coefficient (5(2)P(3/2) --> 5(2)P(1/2)) of 1.25(9)x10(-32) cm(6)/s at 22 degrees C.
authors.affiliation: Laser and Optics Research Center, U.S. Air Force Academy Department of Physics, USAF Academy, Colorado 80840, USA. jerry.sell@usafa.edu
authors.forename: J F
authors.initials: JF
authors.lastname: Sell
authors.forename: M A
authors.initials: MA
authors.lastname: Gearba
authors.forename: B M
authors.initials: BM
authors.lastname: Patterson
authors.forename: T
authors.initials: T
authors.lastname: Genda
authors.forename: B
authors.initials: B
authors.lastname: Naumann
authors.forename: R J
authors.initials: RJ
authors.lastname: Knize