Bringing weak transitions to light
Weak transitions between quantum states are of fundamental importance for a broad range of phenomena from analytical biochemistry to precision physics, but generally challenge experimental detection. Due to their small cross sections scaling with the absolute square of their transition matrix elements, spectroscopic measurements often fail in particular in the presence of competing background processes. Here we introduce a general concept to break this scaling law and enhance the transition probability by exploiting a stronger laser-coupled pathway to the same excited state. We demonstrate the concept experimentally by attosecond transient absorption spectroscopy in helium atoms. The quasi-forbidden transitions from the ground state 1s<sup>2</sup> to the weakly coupled doubly excited 2p3d and sp<sub>2,4-</sub> states are boosted by an order of magnitude. Enhancing single-photon-suppressed transitions can find widespread applicability, from spectral diagnostics of complex molecules in life and chemical sciences to precision spectroscopy of weak transitions in metastable atomic nuclei in the search for new physics.
Authors
- Yu He (ORCID: https://orcid.org/0000-0001-5212-0176)
- Kenneth J. Schäfer (ORCID: https://orcid.org/0000-0003-4740-9113)
- Maximilian Hartmann (ORCID: https://orcid.org/0000-0002-6494-9368)
- Xiao‐Min Tong
- Shuyuan Hu
- Veit Stooß (ORCID: https://orcid.org/0000-0003-3165-2741)
- Thomas Pfeifer (ORCID: https://orcid.org/0000-0002-5312-3747)
- Gergana D. Borisova (ORCID: https://orcid.org/0000-0003-3558-3093)
- Chunhai Lyu (ORCID: https://orcid.org/0000-0001-9444-6385)
- Christian Ott (ORCID: https://orcid.org/0000-0003-4110-0916)
- Mette B. Gaarde (ORCID: https://orcid.org/0000-0002-7815-5534)
- Christoph H. Keitel (ORCID: https://orcid.org/0000-0002-1984-1470)
- Zoltán Harman
- Hao Liang (ORCID: https://orcid.org/0000-0002-5709-2634)
Institutions
- Louisiana State University (US)
- University of Tsukuba (JP)
- Max Planck Institute for the Physics of Complex Systems (DE)
- Max Planck Institute for Nuclear Physics (DE)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-06-20
- DOI
- https://doi.org/10.1038/s41467-025-60701-9
- Citations
- 1
- Primary Topic
- Laser-Matter Interactions and Applications
- Type
- article
- Field-Weighted Citation Impact
- 1.25
Funders
- U.S. Department of Energy
- University of Tsukuba
- Office of Science
- Japan Society for the Promotion of Science
- Basic Energy Sciences