Optical transitions near the elusive 5s-4 f level crossing in highly charged osmium with sensitivity to physics beyond the standard model

N. Rehbehn, L. P. Kozhiparambil Sajith, M. K. Rosner, C. Cheung, S. G. Porsev, M. S. Safronova, S. Worm, D. Budker, T. Pfeifer, J. R. Crespo López-Urrutia, and H. Bekker
Physical Review A 112, L061101 (2025)

Enhanced One-Color-Two-Photon Resonant Ionization in Highly Charged Ions by Fine-Structure Effects

M. Togawa, C. Lyu, C. Shah, M. Botz, J. Goes, J. Danisch, M. Maxton, K. Köbnick, F. Grilo, P. Amaro, K. Kubicek, M. Sekkal, A. Mohamed, R. Boll, A. De Fanis, S. Dold, T. Mazza, J. Montano, N. Rennhack, B. Senfftleben, S. Usenko, Z. Harman, C. H. Keitel, M. Leutenegger, M. Meyer, T. Pfeifer, J. R. Crespo López-Urrutia, and T. M. Baumann
Physical Review Letters 135, 223003 (2025)
 MPIK press release: 100-fold efficiency boost for photoionisation
 MPIK-Pressemitteilung: 100-fache Effizienzsteigerung für Photoionisation
 Phys.org: Rapid X-ray pulses enable 100-fold efficiency boost for photoionization
 Interesting Engineering: World’s most powerful X-ray laser makes krypton absorb 100x more light for double core-hole
 pro-physik.de: 100-fache Effizienzsteigerung für die Photoionisation

A cryogenic Paul trap for probing the nuclear isomeric excited state ^229mTh³⁺

D. Moritz, K. Scharl, M. Wiesinger, G. Holthoff, T. Teschler, M. I. Hussain, J. R. Crespo Lopez-Urrutia, T. Dickel, S. Ding, C. E. Düllmann, E. R. Hudson, S. Kraemer, L. Löbell, C. Mokry, J. Runke, B. Seiferle, L. von der Wense, F. Zacherl, and P. G. Thirolf
The European Physical Journal D 79, 127 (2025)

Finding the Ultranarrow ³P₂ → ³P₀ Electric Quadrupole Transition in Ni¹²⁺ Ion for an Optical Clock

C. Cheung, S. G. Porsev, D. Filin, M. S. Safronova, M. Wehrheim, L. J. Spieß, S. Chen, A. Wilzewski, J. R. Crespo López-Urrutia, and P. O. Schmidt
Physical Review Letters 135, 093002 (2025)

Excited-State Magnetic Properties of Carbon-like Ca¹⁴⁺

L. J. Spieß, S. Chen, A. Wilzewski, M. Wehrheim, J. Gilles, A. Surzhykov, E. Benkler, M. Filzinger, M. Steinel, N. Huntemann, C. Cheung, S. G. Porsev, A. I. Bondarev, M. S. Safronova, J. R. Crespo López-Urrutia, and P. O. Schmidt
Physical Review Letters 135, 043002 (2025)

Comprehensive Laboratory Benchmark of K-shell Dielectronic Satellites of Fe xxv–xxi Ions

C. Shah, P. Amaro, F. Grilo, M. F. Gu, L. Gu, J. P. Santos, F. S. Porter, T. Pfeifer, M. A. Leutenegger, and J. R. Crespo López-Urrutia
The Astrophysical Journal 987, 36 (2025)

Nonlinear Calcium King Plot Constrains New Bosons and Nuclear Properties

A. Wilzewski, L. J. Spieß, M. Wehrheim, S. Chen, S. A. King, P. Micke, M. Filzinger, M. R. Steinel, N. Huntemann, E. Benkler, P. O. Schmidt, L. I. Huber, J. Flannery, R. Matt, M. Stadler, R. Oswald, F. Schmid, D. Kienzler, J. Home, D. P.. Aude Craik, M. Door, S. Eliseev, P. Filianin, J. Herkenhoff, K. Kromer, K. Blaum, V. A. Yerokhin, I. A. Valuev, N. S. Oreshkina, C. Lyu, S. Banerjee, C. H. Keitel, Z. Harman, J. C. Berengut, A. Viatkina, J. Gilles, A. Surzhykov, M. K. Rosner, J. R. Crespo López-Urrutia, J. Richter, A. Mariotti, and E. Fuchs
Physical Review Letters 134, 233002 (2025)
 Physics.aps.org: Searching for a New Force
 Phys.org: Study tightens King plot-based constraints on hypothetical fifth force
 QuantumFrontiers.de: Präzisionsexperimente für die Suche nach einer 5. Kraft
 QuantumFrontiers.de: Precision experiments in the search for a 5th force
 SFB 1227 DQ-mat: Präzisionsexperimente für die Suche nach einer 5. Kraft
 SFB 1227 DQ-mat: Precision experiments in the search for a 5th force
 Isoquant-heidelberg.de: Nonlinear Calcium King Plot Constrains New Bosons and Nuclear Properties
 Popularmechanics.com: Physicists Found a New Clue That Could Reveal the Fifth Force
 Futurezone.de: Grenzen der Physik gesprengt? Forscher finden Hinweis auf bislang unbekannte Kraft
 MPIK-Pressemitteilung: Mit vereinten Kräften auf der Suche nach neuer Physik
 MPIK press release: Joint effort in the search for new physics
 Ethz.ch: Knifflige Suche nach einer neuen Kraft
 Ethz.ch: Elaborate search for a new force

Testing interelectronic interaction in lithium-like tin

J. Morgner, V. A. Yerokhin, C. König, F. Heiße, B. Tu, T. Sailer, B. Sikora, Z. Harman, J. R. Crespo Lopez-Urrutia, C. H. Keitel, S. Sturm, and K. Blaum
Science 388, 6750, 945-949 (2025)
 MPIK press release: Listening to electrons talk: g-factor measurement of lithium-like tin
 MPIK-Pressemitteilung: Elektronen im Gespräch belauscht: Messung des g-Faktors von lithiumhaltigem Zinn
 Phys.org: Listening to electrons 'talk': Lithium-like tin's g-factor measured with 0.5 parts per billion experimental accuracy
 ScienceDaily: Listening to electrons talk: g-factor measurement of lithium-like tin
 idw-Pressemitteilung: Elektronen im Gespräch belauscht: Messung des g-Faktors von lithiumhaltigem Zinn
 Physik in unserer Zeit: Quantenelektrodynamik: Standardmodell im Stresstest

Laboratory X-ray astrophysics at ultrabrilliant light sources with PolarX-EBIT

S. Bernitt, S. Kühn, M. Togawa, R. Steinbrügge, C. Shah, M.. Leutenegger, P. Micke, T. Stöhlker, and J. R. Crespo López-Urrutia
Journal of Instrumentation 20, C03030 (2025)

Hanle effect for lifetime analysis: Li-like ions

J. Richter, M. Togawa, J. R. Crespo López-Urrutia, and A. Surzhykov
Journal of Instrumentation 20, C03003 (2025)

Domain formation and structural stabilities in mixed-species Coulomb crystals induced by sympathetically cooled highly charged ions

L.. Rüffert, E. A. Dijck, L. Timm, J. R. Crespo López Urrutia, and T. E. Mehlstäubler
Physical Review A 110, 063110 (2024)

Identification of highly forbidden optical transitions in highly charged ions

S. Chen, L. J. Spieß, A. Wilzewski, M. Wehrheim, K. Dietze, I. Vybornyi, K. Hammerer, J. R. Crespo López-Urrutia, and P. O. Schmidt
Physical Review Applied 22, 054059 (2024)

Measurement of differential collisional excitation cross sections for the Kα emission of He-like oxygen

F. Grilo, C. Shah, J. Marques, J. P. Santos, J. R. Crespo López-Urrutia, and P. Amaro
Physical Review A 110, 042827 (2024)

Pr¹⁰⁺ as a candidate for a high-accuracy optical clock for tests of fundamental physics

S. G. Porsev, C. Cheung, M. S. Safronova, H. Bekker, N.. Rehbehn, J. R. Crespo López Urrutia, and S. M. Brewer
Physical Review A 110, 042823 (2024)

Hanle Effect for Lifetime Determinations in the Soft X-Ray Regime

M. Togawa, J. Richter, C. Shah, M. Botz, J. Nenninger, J. Danisch, J. J. Goes, S. Kühn, P. Amaro, A. Mohamed, Y. Amano, S. Orlando, R. Totani, M. de Simone, S. Fritzsche, T. Pfeifer, M. Coreno, A. Surzhykov, and J. R. Crespo López-Urrutia
Physical Review Letters 133, 163202 (2024)

High-accuracy measurements of core-excited transitions in light Li-like ions

M. Togawa, S. Kühn, C. Shah, V. A. Zaytsev, N. S. Oreshkina, J. Buck, S. Bernitt, R. Steinbrügge, J. Seltmann, M. Hoesch, C. H. Keitel, T. Pfeifer, M. A. Leutenegger, and J. R. Crespo López-Urrutia
Physical Review A 110, L030802 (2024)

Laboratory Benchmark of n ≥ 4 Dielectronic Recombination Satellites of Fe XVII

G. J. Grell, M. A. Leutenegger, P. Amaro, J. R. Crespo López-Urrutia, and C. Shah
The Astrophysical Journal 971, 78 (2024)

High-precision Transition Energy Measurements of Neon-like Fe XVII Ions

C. Shah, M. Togawa, M. Botz, J. Danisch, J. J. Goes, S. Bernitt, M. Maxton, K. Köbnick, J. Buck, J. Seltmann, M. Hoesch, M. F. Gu, F. S. Porter, T. Pfeifer, M. A. Leutenegger, C. Cheung, M. S. Safronova, and J. R. Crespo López-Urrutia
The Astrophysical Journal 969, 52 (2024)

Natural-linewidth measurements of the 3C and 3D soft-x-ray transitions in Ni XIX

C. Shah, S. Kühn, S. Bernitt, R. Steinbrügge, M. Togawa, L. Berger, J. Buck, M. Hoesch, J. Seltmann, M. G. Kozlov, S. G. Porsev, M. F. Gu, F. S. Porter, T. Pfeifer, M. A. Leutenegger, C. Cheung, M. S. Safronova, and J. R. Crespo López-Urrutia
Physical Review A 109, 063108 (2024)

Experimental and theoretical Ritz–Rydberg analysis of the electronic structure of highly charged ions of lead and bismuth by optical spectroscopy

M. K. Rosner, N. Rehbehn, and J. R. Crespo López-Urrutia
Journal of Physics B 57, 055001 (2024)

Narrow and Ultranarrow Transitions in Highly Charged Xe Ions as Probes of Fifth Forces

N. Rehbehn, M. K. Rosner, J. C. Berengut, P. O. Schmidt, T. Pfeifer, M. F. Gu, and J. R. Crespo López-Urrutia
Physical Review Letters 131, 161803 (2023)

Stringent test of QED with hydrogen-like tin

J. Morgner, B. Tu, C. M. König., T. Sailer, F. Heiße, H. Bekker, B. Sikora, C. Lyu, V. A. Yerokhin, Z. Harman, J. R. Crespo López-Urrutia, C. H. Keitel, S. Sturm, and K. Blaum
Nature 622, 53-57 (2023)
 MPIK press release: Precise testing of quantum electrodynamics
 MPIK-Pressemitteilung: Quantenelektrodynamik auf dem Prüfstand
 MPG press release: When the laws of physics are at stake - Quantum electrodynamics put to the test
 MPG-Presssemitteilung: Wenn Gesetze der Physik auf dem Spiel stehen - Quantenelektrodynamik auf dem Prüfstand
 Nature research briefings: Testing the limits of the standard model of particle physics with a heavy, highly charged ion
 phys.org: A precise test of quantum electrodynamics: Measuring the g factor of electrons in hydrogen-like tin

Sympathetically cooled highly charged ions in a radio-frequency trap with superconducting magnetic shielding

E. A. Dijck, C. Warnecke, M. Wehrheim, R. B. Henninger, J. Eff, K. Georgiou, A. Graf, S. Kokh, L. P. Kozhiparambil Sajith, C. Mayo, V. M. Schäfer, C. Volk, P. O. Schmidt, T. Pfeifer, and J. R. Crespo López-Urrutia
Review of Scientific Instruments 94, 083203 (2023)

Photoelectron tomography with an intra-cavity velocity-map imaging spectrometer at 100 MHz repetition rate Open Access

J.. Oelmann, T. Heldt, L. Guth, J. Nauta, N. Lackmann, V. Wössner, S. Kokh, T. Pfeifer, and J. R. Crespo López-Urrutia
Review of Scientific Instruments 93, 123303 (2022)

New Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem

S. Kühn, C. Cheung, N. S. Oreshkina, R. Steinbrügge, M. Togawa, S. Bernitt, L. Berger, J. Buck, M. Hoesch, J. Seltmann, F. Trinter, C. H. Keitel, M. G. Kozlov, S. G. Porsev, M. F. Gu, F. S. Porter, T. Pfeifer, M. A. Leutenegger, Z. Harman, M. S. Safronova, J. R. Crespo López-Urrutia, and C. Shah
Physical Review Letters 129, 245001 (2022)
 Phys. Rev. Lett.: Editors' Suggestion - Open Access
 APS Physics Viewpoint: Getting a Clearer View of Iron Emission Lines
 idw press release: X-ray analysis without doubt - Four-decade enigma of cosmic X-rays solved
 Focus Online: Rätsel im Röntgenspektrum gelöst
 pro-physik.de: Kosmisches Röntgen-Rätsel gelöst
 MPG-Pressemitteilung: Röntgenanalyse ohne Zweifel
 MPIK press release: X-ray analysis without doubt
 MPIK-Pressemitteilung: Röntgenanalyse ohne Zweifel
 Physics Today: Experiment resolves long-standing iron-spectrum discrepancy

X-Ray Photoabsorption of Density-sensitive Metastable States in Ne vii, Fe xxii, and Fe xxiii

R. Steinbrügge, S. Kühn, F. Nicastro, M. F. Gu, M. Togawa, M. Hoesch, J. Seltmann, I. Sergeev, F. Trinter, S. Bernitt, C. Shah, M. A. Leutenegger, and J. R. Crespo López-Urrutia
The Astrophysical Journal 941, 188 (2022)

An optical atomic clock based on a highly charged ion

S. A. King, L. J. Spieß, P. Micke, A. Wilzewski, T. Leopold, E. Benkle, R. Lange, N. Huntemann, A. Surzhykov, V. A. Yerokhin, J. R. Crespo López-Urrutia, and P. O. Schmidt
Nature 611, 43-47 (2022)

X-ray spectra of the Fe-L complex III. Systematic uncertainties in atomic data

L. Gu, C. Shah, J. Mao, A. J. J. Raassen, J. de Plaa, C. Pinto, H. Akamatsu, N. Werner, A. Simionescu, F. Mernier, M. Sawada, P. Mohanty, P. Amaro, M. F. Gu, F. S. Porter, J. R. C. Lopez-Urrutia, and J. S. Kaastra
Astronomy and Astrophysics 664, A62 (2022)

Measuring the stability of fundamental constants with a network of clocks

G. Barontini, L. Blackburn, V. Boyer, F. Butuc-Mayer, X. Calmet, J. R. Crespo Lopez-Urrutia, E. A. Curtis, B. Darquie, J. Dunningham, N. J. Fitch, E. M. Forgan, K. Georgiou, P. Gill, R. M. Godun, J. Goldwin, V. Guarrera, A. C. Harwood, I. R. Hill, R. J. Hendricks, M. Jeong, M. Y. H. Johnson, M. Keller, L. P. Kozhiparambil Sajith, F. Kuipers, H. S. Margolis, C. Mayo, P. Newman, A. O. Parsons, L. Prokhorov, B. I. Robertson, J. Rodewald, M. S. Safronova, B. E. Sauer, M. Schioppo, N. Sherrill, Y. V. Stadnik, K. Szymaniec, M. R. Tarbutt, R. C. Thompson, A. Tofful, J. Tunesi, A. Vecchio, Y. Wang, and S. Worm
EPJ Quantum Technology 9, 12 (2022)

Highly Charged Ions for High-Resolution Soft X-ray Grating Monochromator Optimisation

M. Hoesch, J. Seltmann, F. Trinter, S. Kühn, M. Togawa, R. Steinbrügge, S. Bernitt, and J. R. Crespo López-Urrutia
Journal of Physics: Conference Series 2380, 012086 (2022)

A new benchmark of soft X-ray transition energies of Ne, CO₂, and SF₆: paving a pathway towards ppm accuracy

J. Stierhof, S. Kühn, M. Winter, P. Micke, R. Steinbrügge, C. Shah, N. Hell, M. Bissinger, M. Hirsch, R. Ballhausen, M. Lang, C. Gräfe, S. Wipf, R. Cumbee, G. L. Betancourt-Martinez, S. Park, J. Niskanen, M. Chung, F. S. Porter, T. Stöhlker, T. Pfeifer, G. V. Brown, S. Bernitt, P. Hansmann, J. Wilms, J. R. Crespo López-Urrutia, and M. A. Leutenegger
The European Physical Journal D: Atomic, Molecular and Optical Physics 76, 38 (2022)

Uncertainties in Atomic Data for Modeling Astrophysical Charge Exchange Plasmas

L. Gu, C. Shah, and R. Zhang
Sensors 22, 752 (2022)