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Researchers used a reaction microscope with time-resolved detection to study how lithium atoms become ionized by laser light during optical trapping experiments. They mapped the complete momentum distributions of ejected electrons and identified specific resonant excitation pathways through intermediate atomic states (5p, 5f, and 4d), including an unexpected ionization channel following spontaneous decay from the 5f to 4d state. The ionization efficiency showed strong dependence on laser polarization due to quantum selection rules and interference between different excitation pathways.
Why it matters
This work provides fundamental understanding of photoionization processes that occur during laser cooling and trapping experiments, which are essential techniques in atomic physics research, quantum computing, and precision measurements. The event-by-event detection method demonstrated here could enable more detailed studies of light-matter interactions in ultracold atomic systems.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Abstract: 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.
Source: Resonant photoionization dynamics during optical trapping of lithium atoms