Velocity distributions and second-order Doppler shifts in an optically pumped cesium beam frequency standard

The velocity distribution of cesium atoms in an optically pumped cesium beam frequency standard constructed at the KRISS is obtained by using the Fourier transform of Ramsey lineshape. The velocity distribution fits well with a 1//spl upsi//sup 2/-weighted Maxwellian rather than a 1//spl upsi/-weighted one in our case. The second-order Doppler shift is -2.7/spl times/10/sup -13/.