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High Resolution Extreme Ultraviolet Laser Spectroscopy

Total Cost €


EC-Contrib. €






 XUV-COMB project word cloud

Explore the words cloud of the XUV-COMB project. It provides you a very rough idea of what is the project "XUV-COMB" about.

expansion    energy    2s    nm    investigation    direction    series    co    successful    comb    radiation    nuclear    unexplored    foreseeable    line    unexplained    electrodynamics    structure    anti    discrepancies    hydrogen    precision    atomic    trap    besides    accuracy    locked    spectroscopy    theory    first    quantum    zwith    progress    combine    good    exclusively    ordinary    leaving    representing    hence    modes    disputed    1s    ionized    ultraviolet    item    though    unlike    interesting    spectrum    comparisons    charge    singly    track    performed    photons    ion    suitable    physics    frequency    frontier    essentially    fuelling    discovered    logical    shift    almost    meantime    harmonics    experiment    fails    source    fine    power    muonic    discrete    serious    lamb    levels    pairs    spectroscopic    sympathetically    ions    mode    resolution    ing    experiments    cooled    sharpest    accessible    resonance    beaten    list    constant    eliminates    equation    transition    cooling    experimental    dirac    stored    laser    dominating    qed    extreme    excitation    observation    he    helium    photon    waiting    hitherto    coherent    readily   

Project "XUV-COMB" data sheet

The following table provides information about the project.


Organization address
city: Munich
postcode: 80539

contact info
title: n.a.
name: n.a.
surname: n.a.
function: n.a.
email: n.a.
telephone: n.a.
fax: n.a.

 Coordinator Country Germany [DE]
 Total cost 1˙968˙125 €
 EC max contribution 1˙968˙125 € (100%)
 Programme 1. H2020-EU.1.1. (EXCELLENT SCIENCE - European Research Council (ERC))
 Code Call ERC-2016-ADG
 Funding Scheme ERC-ADG
 Starting year 2017
 Duration (year-month-day) from 2017-06-01   to  2022-05-31


Take a look of project's partnership.

# participants  country  role  EC contrib. [€] 


 Project objective

Discrepancies between theory and experiments have been fuelling the development of physics from the discrete line spectrum of hydrogen, where classical physics fails, to the Lamb shift, which is unexplained by the Dirac equation. At the precision frontier, comparisons between theory and experiment have been performed almost exclusively with atomic hydrogen. To progress from there, it very good accuracy. The spectroscopic investigation of muonic hydrogen, which was successful recently, was the first step in that direction and has brought up a serious challenge to Quantum Electrodynamics (QED). Even though we could solve this problem in the meantime, there might be others waiting to be discovered when leaving the beaten track of ordinary atomic hydrogen. Besides anti-hydrogen, high resolution laser spectroscopy of singly ionized helium is the next logical item on the list. In addition of representing a hitherto unexplored system, He allows for a far better test than atomic hydrogen due to the QED power series expansion of its energy levels in terms of ZWith the nuclear charge Z and the fine structure constant the disputed terms are of the order of (Z)6. Unlike ordinary hydrogen, He can be readily stored in an ion trap and sympathetically cooled by co-stored ions with an accessible cooling transition. This approach eliminates essentially all dominating experimental uncertainties that we face with ordinary hydrogen today. The 1S-2S resonance is the sharpest and hence most interesting transition. Its observation requires highly coherent extreme ultraviolet radiation at 60.8 nm which can be generated through high order harmonics from a mode locked laser. The resulting frequency comb is most suitable for a two-photon transition as photons from pairs of modes combine to deliver the excitation energy. Other applications of such new laser source are foreseeable.


year authors and title journal last update
List of publications.
2019 Byoung-moo Ann, Fabian Schmid, Jonas Krause, Theodor W Hänsch, Thomas Udem, Akira Ozawa
Motional resonances of three-dimensional dual-species Coulomb crystals
published pages: 35002, ISSN: 0953-4075, DOI: 10.1088/1361-6455/aaf5ea
Journal of Physics B: Atomic, Molecular and Optical Physics 52/3 2019-12-17
2019 Fabian Schmid, Johannes Weitenberg, Theodor W. Hänsch, Thomas Udem, Akira Ozawa
Simple phase noise measurement scheme for cavity-stabilized laser systems
published pages: 2709, ISSN: 0146-9592, DOI: 10.1364/ol.44.002709
Optics Letters 44/11 2019-12-17
2018 Akira Ozawa, Josue Davila-Rodriguez, Theodor W. Hänsch, Thomas Udem
Quantum Zeno Effect assisted Spectroscopy of a single trapped Ion
published pages: , ISSN: 2045-2322, DOI: 10.1038/s41598-018-28824-w
Scientific Reports 8/1 2019-04-18

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