title: Precision microwave measurement of the 2(3)P(1)-2(3)P(0) interval in atomic helium: a determination of the fine-structure constant.
abstract: The 2(3)P(1)-to- 2(3)P(0) interval in atomic helium is measured using a thermal beam of metastable helium atoms excited to the 2(3)P state using a 1.08-microm diode laser. The 2(3)P(1)-to- 2(3)P(0) transition is driven by 29.6-GHz microwaves in a rectangular waveguide cavity. Our result of 29,616,950.9+/-0.9 kHz is the most precise measurement of helium 2(3)P fine structure. When compared to precise theory for this interval, this measurement leads to a determination of the fine-structure constant of 1/137.0359864(31).
authors.affiliation: Department of Physics, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3.
authors.forename: M C
authors.initials: MC
authors.lastname: George
authors.forename: L D
authors.initials: LD
authors.lastname: Lombardi
authors.forename: E A
authors.initials: EA
authors.lastname: Hessels