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We report on experimental measurements and theoretical calculations of Rabi oscillation distortion during rubidium clock transition in a compact cold-atom clock. The distortion of the Rabi oscillations of the clock transition caused by the magnetically sensitive transitions between magnetic sublevels is related to the duration and amplitude of the microwave pulse, the density distribution of cold atoms, and the biased magnetic field inside the microwave cavity. The theoretical calculations agreed well with the experimental results. The Rabi oscillation measurements are beneficial for determining the optimal parameters of a cold-atom clock and identifying the uniformity of the microwave field inside the cavity. This measurement can be extended to the atomic fountain clock and the vapor-cell atomic clock.

The total photodetachment cross section of a negative ion near a repulsive center is studied based on the closed-orbit theory. An analytical expression, written as a product of the zero-field photodetachment cross section and a modulation function, is obtained for energy above and below threshold. The expression also incorporates the different wave sources produced by different negative ions. The present results are shown to be accurate by comparing with quantum calculations based on the exact Coulomb Green's function. We also compared the photodetachment cross section near a repulsive center with that in a homogeneous electric field and found interesting connections between the two.

We study the detached-electron flux distributions from the photodetachment of a negative ion near a repulsive center. Using a semiclassical approach, we calculate the electron flux on spherical detectors with various radii. The classically allowed angular range of the interference patterns on the spherical screen increases as the detached-electron energy is increased. In the classically allowed range, we find that there are always two trajectories going from the negative ion to the observation point on the screen, inducing quantum interference patterns. We have also extended the formulas into the tunneling region. The interference patterns also reflect the quantum angular distribution of electrons leaving the ion. A scaling property for the detached-electron flux is investigated. The accuracy of our semiclassical formulas is established by comparison with a quantum treatment using the exact Coulomb Green's function.