title: Observation of cold, long-lived antiprotonic helium ions.
abstract: Cold, two-body antiprotonic helium ions p 4He2+ and p 3He2+ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers ni=28-32 and li=ni-1 have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature T approximately 10 K by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of p 3He2+ against annihilation induced by collisions were shorter than those of p 4He2+, and decreased for larger-ni states.
authors.affiliation: CERN, CH-1211 Geneva 23, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Hori
authors.forename: J
authors.initials: J
authors.lastname: Eades
authors.forename: R S
authors.initials: RS
authors.lastname: Hayano
authors.forename: W
authors.initials: W
authors.lastname: Pirkl
authors.forename: E
authors.initials: E
authors.lastname: Widmann
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: H A
authors.initials: HA
authors.lastname: Torii
authors.forename: B
authors.initials: B
authors.lastname: Juhász
authors.forename: D
authors.initials: D
authors.lastname: Horváth
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Yamazaki