title: Ultrafast dynamics of neutral superexcited oxygen: a direct measurement of the competition between autoionization and predissociation.
abstract: Using ultrafast extreme ultraviolet pulses, we performed a direct measurement of the relaxation dynamics of neutral superexcited states corresponding to the nlσ(g)(c(4)Σ(u)(-)) Rydberg series of O(2). An extreme ultraviolet attosecond pulse train was used to create a temporally localized Rydberg wave packet and the ensuing electronic and nuclear dynamics were probed using a time delayed femtosecond near-infrared pulse. We investigated the competing predissociation and autoionization mechanisms in superexcited oxygen molecules and found that autoionization is dominant for the low n Rydberg states. We measured an autoionization lifetime of 92±6 fs and 180±10 fs for the (5s,4d)σ(g) and (6s,5d)σ(g) Rydberg state groups, respectively. We also determine that the disputed neutral dissociation lifetime for the ν=0 vibrational level of the Rydberg series is 1100±100 fs.
authors.affiliation: Department of Physics, University of Arizona, Tucson, Arizona 85721, USA. timmers@physics.arizona.edu
authors.forename: Henry
authors.initials: H
authors.lastname: Timmers
authors.forename: Niranjan
authors.initials: N
authors.lastname: Shivaram
authors.forename: Arvinder
authors.initials: A
authors.lastname: Sandhu