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Updated: Jan 8, 2026

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Direct Measurement of 4f-4f Transitions and Electronic Hot Bands in Lanthanoid-Antenna Complexes by Helium-Tagging
Simran Baweja1, Manfred M Kappes1,2, Alexander Schäfer1
1Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
Abstract:
Lanthanoid-antenna complexes are promising building blocks for quantum technologies, yet their potential in the condensed phase is often obscured by phonon-induced decoherence. This article reports the first one-color helium-tagging spectroscopic measurements of isolated [Ho(enpypa)]+ and [Yb(enpypa)]+ complexes (enpypa = ethylenediamine-pyridine-picolinic acid) at cryogenic temperatures, directly resolving their elusive 4f-4f excitations in the gas phase. For Ho3+, at least eight Stark-split multiplets are identified across the visible spectrum, while the Yb3+ complex exhibits a sharp 2F7/2 → 2F5/2 near-infrared manifold together with a hot band consistent with thermal equilibrium at 4 K. The UV-absorbing ligand shows depletion cross sections over two orders of magnitude larger than the lanthanoid-centered transitions, highlighting the sensitivity and dynamic range of our next-generation apparatus. These results establish cryogenic ion trap spectroscopy as a powerful tool for probing lanthanoid photophysics and pave the way for multicolor spectroscopic investigations of lanthanoid systems tailored for quantum information science.
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