Photoionization induced by trapping and auxiliary laser fields is an inherent feature of many laser-cooling and optical trapping experiments, yet its microscopic dynamics are rarely investigated directly. In this work, we employ a reaction microscope implementing an event-by-event photoionization time retrieval technique to extend momentum-resolved photoelectron spectroscopy to continuous-wave laser--atom interactions. We investigate low-intensity multicolor photoionization of laser-cooled lithium atoms confined in an all-optical trap. Complete three-dimensional electron momentum distributions and kinetic-energy spectra recorded for different laser wavelengths and polarization configurations identify resonant excitation of the
5p and
5f states and reveal an additional ionization channel following spontaneous decay from the
5f to the
4d state. A pronounced polarization dependence of the photoionization yield is explained by magnetic-sublevel selection rules and the coherent interference of different virtual excitation pathways. These results demonstrate that reaction microscopy combined with event-by-event time reconstruction provides a powerful approach for investigating microscopic electronic dynamics in laser-cooled atomic systems and offers new insight into photoionization processes occurring during optical trapping.
We report experimental results on the photoionization spectra of excited sodium atoms in a well-defined
ml=1 substate in the presence of a dc electric field. The various spectra corresponding to a definite polarization of the ionizing light exhibit characteristic features. It appears in addition that they are strikingly perturbed by the Earth's magnetic field.
A quasihydrogenic complete diamagnetic manifold is investigated experimentally. The spectra are obtained in a uniform magnetic field by exciting in a one-step process, using polarised laser light, the lithium atoms of an atomic beam. The whole structure of the M=0 odd diamagnetic multiplet has been recorded for the first time. This experiment provides a confirmation for the existence of the two classes of states predicted for the diamagnetic Hamiltonian of atomic hydrogen in the weak-field limit. The fundamental features of diamagnetism still subsist for such high field strengths so that the diamagnetic interaction cannot be regarded as a perturbation with respect to the Coulomb problem. The intermanifold coupling and the influence of effects due to the ionic core in the lithium atom are evaluated quantitatively.