Measurement of Electric-Dipole Moment by Polarization Laser Spectroscopy

Laser-induced atomic excitation is a key physical process widely used in such technology fields as laser isotope separation and laser quantitative analysis. The quantity which characterizes this process is primarily the electric-dipole moment μ. We propose a new method of measuring the value of μ accurately for transitions between two degenerate levels, which exploits the strong polarization dependence of the atomic photo-excitation behavior. In a vacuum chamber the two-step resonance excitation of atoms is achieved with two laser beams. We control the polarizations of the lasers and realize different excitation conditions in the same excitation scheme. By doing quantum mechanical calculation with μ in it as a parameter, we fit the different excitation curves simultaneously to obtain the most probable value of μ. The applicability of the method is demonstrated for two types of excitation schemes in uranium atom. The values of μ for transitions from the 16,900cm −1 level to the 33,939 and 34,599cm −1 level proved to be 0.16 and 4.1 Debye, respectively. Direct measurement of these values has not been reported up to now. The result proved to be appropriate in comparisons with values obtained by an independent method based on the AC Stark effect.