1. Hanle effect for lifetime determinations in the soft X-ray regime
- Author
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Togawa, Moto, Richter, Jan, Shah, Chintan, Botz, Marc, Nenninger, Joshua, Danisch, Jonas, Goes, Joschka, Kühn, Steffen, Amaro, Pedro, Mohamed, Awad, Amano, Yuki, Orlando, Stefano, Totani, Roberta, de Simone, Monica, Fritzsche, Stephan, Pfeifer, Thomas, Coreno, Marcello, Surzhykov, Andrey, and López-Urrutia, José R. Crespo
- Subjects
Physics - Atomic Physics - Abstract
By exciting a series of $1\mathrm{s}^{2}\, ^{1}\mathrm{S}_{0} \to 1\mathrm{s}n\mathrm{p}\, ^{1}\mathrm{P}_{1}$ transitions in helium-like nitrogen ions with linearly polarized monochromatic soft X-rays at the Elettra facility, we found a change in the angular distribution of the fluorescence sensitive to the principal quantum number $n$. In particular it is observed that the ratio of emission in directions parallel and perpendicular to the polarization of incident radiation increases with higher $n$. We find this $n$-dependence to be a manifestation of the Hanle effect, which served as a practical tool for lifetime determinations of optical transitions since its discovery in 1924. In contrast to traditional Hanle effect experiments, in which one varies the magnetic field and considers a particular excited state, we demonstrate a 'soft X-ray Hanle effect' which arises in a static magnetic field but for a series of excited states. By comparing experimental data with theoretical predictions, we were able to determine lifetimes ranging from hundreds of femtoseconds to tens of picoseconds of the $1\mathrm{s}n\mathrm{p}\, ^{1}\mathrm{P}_{1}$ levels, which find excellent agreement with atomic-structure calculations. We argue that dedicated soft X-ray measurements could yield lifetime data that is beyond current experimental reach and cannot yet be predicted with sufficient accuracy., Comment: 7 pages, 4 figures
- Published
- 2024