Optical frequency measurements of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline">mml:mrowmml:mn6mml:mis<mml:mspace width="0.2em" />mml:mmultiscriptsmml:miSmml:mrowmml:mn1mml:mo∕mml:mn2<mml... (original) (raw)

High resolution laser spectroscopy of the 6s 2 S 1/2 → 6p 2 P 1/2 transition ͑D 1 line͒ in neutral 133 Cs is performed in a highly collimated thermal atomic beam by use of a femtosecond laser frequency comb and narrow-linewidth diode laser. The diode laser is offset locked to a single frequency component of the femtosecond laser frequency comb and probes the optical transitions between selected pairs of ground-state and excited-state hyperfine components. A photodiode detects the excited-state decay fluorescence, and a computerized data acquisition system records the signal. The Doppler shift is eliminated by orienting the laser beam in a direction perpendicular to the atomic beam to within a precision of 5 ϫ 10 −6 rad. Optical frequencies for all four pairs of hyperfine components are measured independently, from which the D 1 line centroid and excitedstate hyperfine splitting are obtained by least-squares minimization with the ground-state splitting as a fixed constraint. We find the D 1 line centroid to be f D 1 = 335 116 048 748.1͑2.4͒ kHz, and the 6p 2 P 1/2 state hyperfine splitting to be 1 167 723.6͑4.8͒ kHz. These results, in combination with the results of an atom interferometry experiment by Wicht et al. ͓Phys. Scripta T 102, 82 ͑2002͔͒, are used to calculate a new value for the fine-structure constant.