Velocity distributions from the Fourier transforms of Ramsey line shapes

A computerized method for finding velocity distributions from the Fourier transforms of Ramsey line shapes has been developed. Ramsey lineshape data taken at different excitation powers is used; a weighted average of data from three powers gives satisfactory results. The excitation amplitude parameter b is found by minimizing a quality-of-fit criterion. The method is limited to long standards by the assumption that the excitation length l is much less than the drift region length L. However, the addition of first order l/L corrections to the theory make the method usable for shorter standards. The method has been successfully tested with lineshapes theoretically generated from known velocity distributions