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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.

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

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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