title: Hyperfine structure of antiprotonic helium revealed by a laser-microwave-laser resonance method.
abstract: Using a newly developed laser-microwave-laser resonance method, we observed a pair of microwave transitions between hyperfine levels of the (n,L)=(37,35) state of antiprotonic helium. This experiment confirms the quadruplet hyperfine structure arising from the interaction of the antiproton orbital angular momentum, the electron spin and the antiproton spin as predicted by Bakalov and Korobov. The measured frequencies of nu(+)(HF)=12.895 96+/-0.000 34 GHz and nu(-)(HF)=12.924 67+/-0.000 29 GHz agree with recent theoretical calculations on a level of 6x10(-5).
authors.affiliation: Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Widmann
authors.forename: J
authors.initials: J
authors.lastname: Eades
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: J
authors.initials: J
authors.lastname: Sakaguchi
authors.forename: T
authors.initials: T
authors.lastname: Tasaki
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: R S
authors.initials: RS
authors.lastname: Hayano
authors.forename: M
authors.initials: M
authors.lastname: Hori
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: T
authors.initials: T
authors.lastname: Yamazaki