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arXiv:2604.07283 · Physical Review Research

Two-dimensional shelving spectroscopy of ultraviolet ground state transitions in dysprosium

Kevin S. H. Ng, Paul Uerlings, Fiona Hellstern, Jens Hertkorn, Luis Weiß, Stephan Welte, Tilman Pfau, Ralf Klemt

physics.atom-phcond-mat.quant-gasquant-phSubmitted Apr 8, 2026• Announced Apr 9, 2026• 0 citations• Revised Apr 28, 2026 (v2)
v1 · Apr 8, 2026v2 · Apr 28, 2026
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Abstract

The open inner-shell electronic structure of lanthanides with large magnetic moments gives rise to a rich spectrum of transitions available for laser cooling, trapping, and coherent control. Despite this, the large number of ultraviolet (UV) transitions below 400nm have so far been rarely utilized in dipolar atom experiments. Here, we investigate multiple UV ground state transitions in dysprosium. Several of these UV excited states have the largest decay strengths to the ultralong-lived, low-lying first excited state which are comparable to the most commonly used strongest transitions found in dipolar atoms. Using two-dimensional shelving spectroscopy which improves detection sensitivity and provides a straightforward way to determine the hyperfine-isotope structure and excited state total angular momentum $J$, we measure isotope shifts, hyperfine coefficients, and create King plots to determine their electronic nature. Such knowledge of these UV transitions which analogously exist in other magnetic atoms is important for optically populating the first excited state and can be used towards creating an optical clock, high resolution imaging in quantum gas microscopy, and probing lanthanide nuclei with enhanced Schiff moments in search of physics beyond the standard model.

Comments
9 pages, 4 figures, 7 pages supplementary material

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The open inner-shell electronic structure of lanthanides with large magnetic moments gives rise to a rich spectrum of transitions available for laser cooling, trapping, and coherent control. Despite this, the large number of ultraviolet (UV) transitions below 400nm have so far been rarely utilized in dipolar atom experiments. Here, we investigate multiple UV ground state transitions in dysprosium. Several of these UV excited states have the largest decay strengths to the ultralong-lived, low-lying first excited state which are comparable to the most commonly used strongest transitions found in dipolar atoms. Using two-dimensional shelving spectroscopy which improves detection sensitivity and provides a straightforward way to determine the hyperfine-isotope structure and excited state total angular momentum JJJ, we measure isotope shifts, hyperfine coefficients, and create King plots to determine their electronic nature. Such knowledge of these UV transitions which analogously exist in other magnetic atoms is important for optically populating the first excited state and can be used towards creating an optical clock, high resolution imaging in quantum gas microscopy, and probing lanthanide nuclei with enhanced Schiff moments in search of physics beyond the standard model.
Molecules containing a lanthanide atom have sets of electronic states arising from excitation of an inner-shell electron. These states have received little attention but are thought to play an important role in laser cooling of such molecules and may be a useful resource for testing fundamental physics. We study a series of inner-shell excited states in YbF using resonance-enhanced multiphoton ionization spectroscopy. We investigate the excited states of lowest energy, 8474, 9013, and 9090 cm−1 above the ground state, all corresponding to the configuration 4f136s2 F27/2 of the Yb+ ion. They are metastable, since they have no electric dipole allowed transitions to the ground state. We also characterize a state at 31 050 cm−1 that is easily excited from both the ground and metastable states, which makes it especially useful for this spectroscopic study. Finally, we study two states at 48 720 and 48 729 cm−1 , which are above the ionization limit and feature strong autoionizing resonances that prove useful for efficient detection of the molecules and for identifying the rotational quantum number of each line in the spectrum. We resolve the rotational structures of all these states and find that they can all be described by a very simple model based on Hund’s case (c). Our study provides information necessary for laser slowing and magneto-optical trapping of YbF, which is an important species for testing fundamental physics. We also consider whether the low-lying inner-shell states may themselves be useful as probes of the electron’s electric dipole moment or of varying fundamental constants, since they are long-lived states in a laser-coolable molecule featuring closely spaced levels of opposite parity. Published by the American Physical Society 2024
Open-shell lanthanide atoms, and dysprosium in particular, combine a large ground-state angular momentum with dense electronic spectra, making their dynamical polarizability strongly dependent on wavelength and internal state, and therefore challenging to calculate and characterize experimentally. This issue has become especially relevant with the recent development of single-atom trapping of dysprosium in optical-tweezer arrays, where precise knowledge of the polarizability is needed to design optimized trapping architectures. Here, we exploit the strong spin-dependent light shift near the J′=J−1J'=J-1J′=J−1 intercombination line at 530.306 nm to determine the background scalar and vector polarizabilities of 162^{162}162Dy in its ground state near this wavelength. Our measurements quantitatively agree with atomic-structure calculations and provide new insight into the contributions of nearby transitions in a spectral region relevant to emerging dysprosium tweezer platforms.
Lanthanides, like erbium and dysprosium, have emerged as powerful platforms for quantum-gas research due to their diverse properties, including a significant large spin manifold in their absolute ground state. However, effectively exploiting the spin richness necessitates precise manipulation of spin populations, a challenge yet to be fully addressed in this class of atomic species. In this work, we present an all-optical method for deterministically controlling the spin composition of a dipolar bosonic erbium gas, based on a clocklike transition in the telecom window at 1299 n m . The atoms can be prepared in just a few tens of microseconds in any spin-state composition using a sequence of Rabi-pulse pairs, selectively coupling Zeeman sublevels of the ground state with those of the long-lived clocklike state. Finally, we demonstrate that this transition can also be used to create spin-selective light shifts, thus fully suppressing spin-exchange collisions. These experimental results unlock exciting possibilities for implementing advanced spin models in isolated, clean, and fully controllable lattice systems. Published by the American Physical Society 2024
We have measured and analyzed the hyperfine structure of two lines, one at 583 nm and one at 401 nm, of the only stable fermionic isotope of atomic erbium as well as determined its isotope shift relative to the four most-abundant bosonic isotopes. Our work focuses on the $J\ensuremath{\rightarrow}J+1$ laser cooling transitions from the [Xe]4f126s2(3H6)[\text{Xe}]4{f}^{12}6{s}^{2}{(}^{3}{H}_{6})[Xe]4f126s2(3H6​) ground state to two levels of the excited [Xe]4f126s6p[\text{Xe}]4{f}^{12}6s6p[Xe]4f126s6p configuration, which are of major interest for experiments on quantum degenerate dipolar Fermi gases. From a fit to the observed spectra of the strong optical transition at 401 nm we find that the magnetic dipole and electric quadrupole hyperfine constants for the excited state are ${A}_{e}/h=\ensuremath{-}100.1(3)\phantom{\rule{0.28em}{0ex}}\mathrm{MHz}$ and ${B}_{e}/h=\ensuremath{-}3079(30)\phantom{\rule{0.28em}{0ex}}\mathrm{MHz}$, respectively. The hyperfine spectrum of the narrow transition at 583 nm, was previously observed and accurate Ae{A}_{e}Ae​ and Be{B}_{e}Be​ coefficients are available. A simulated spectrum based on these coefficients agrees well with our measurements. We have also determined the hyperfine constants using relativistic configuration-interaction ab initio calculations. The agreement between the ab initio and fitted data for the ground state is better than 0.1%, while for the two excited states the agreement is 1% and 11% for the Ae{A}_{e}Ae​ and Be{B}_{e}Be​ constants, respectively.
Ultracold dysprosium gases, with a magnetic moment 10 times that of alkali atoms and equal only to terbium as the most magnetic atom, are expected to exhibit a multitude of fascinating collisional dynamics and quantum dipolar phases, including quantum liquid crystal physics. We report the first laser cooling and trapping of half a billion Dy atoms using a repumper-free magneto-optical trap (MOT) and continuously loaded magnetic confinement, and we characterize the trap recycling dynamics for bosonic and fermionic isotopes. The first inelastic collision measurements in the few partial wave, 100 microK-1 mK, regime are made in a system possessing a submerged open electronic f shell. In addition, we observe unusual stripes of intra-MOT <10 microK sub-Doppler cooled atoms.
Highly excited Rydberg states of lanthanides are a promising, yet largely unexplored, playground for quantum studies. Here, we report on the first high-resolution spectroscopy of 162Dy obtained by two-color trap depletion spectroscopy in a magneto-optical trap. The absolute excitation frequency of over 700 states with effective principal quantum number n between 21 and 130 is measured with an accuracy of 20 MHz. Most states are assigned to the 8 different series converging to the first 4f10(5I8)6s(2S1/2) J = 17/2 ionization potential. This energy is measured at EIP = 47901.8265 +/- 0.0008 cm-1, improving the precision of the literature value by over an order of magnitude. A multichannel quantum defect theory approach is used to benchmark and refine the assignments and to characterize six observed perturbing states belonging to higher ionization limits. These results pave the way for using dysprosium in Rydberg-based quantum architectures, leveraging the unique properties arising from its complex electronic structure. They also represent a compelling benchmark for ab-initio calculations of open-shell atomic systems.