Precision microwave measurement of the 23P1-23P0 interval in atomic helium:: A determination of the fine-structure constant -: art. no. 173002

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-mum diode laser. The 2(3)P(1)-to-P-23(0) transition is driven by 29.6-GHz microwaves in a rectangular waveguide cavity. Our result of 29616950.9 +/- 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 1/137.035 986 4(31).