title: Precision microwave measurement of the 2 3P1-2 3P2 interval in atomic helium
abstract: The 2 3P1-to- 2 3P2 interval in atomic helium is measured using a thermal beam of metastable helium atoms excited to the 2 3P state using a 1.08-&mgr;m diode laser. The 2 3P1-to- 2 3P2 transition is driven by 2.29-GHz microwaves in a coaxial transmission line. Our result of 2 291 174.0+/-1.4 kHz is the most precise measurement of helium 2 3P fine structure. This measurement plays a key role in obtaining a new value for the fine-structure constant.
authors.affiliation: Department of Physics, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3.
authors.initials: CH
authors.lastname: Storry
authors.initials: MC
authors.lastname: George
authors.initials: EA
authors.lastname: Hessels