X-ray laser spectroscopy of highly charged ions at FLASH

Epp, Sascha W.; López‐Urrutia, J. R. Crespo; Simon, M. C.; Baumann, T.; Brenner, Günter; Ginzel, R.; Guerassimova, N.; Mäckel, V.; Mokler, P. H.; Schmitt, B.; Tawara, H.; Ullrich, J.

doi:10.1088/0953-4075/43/19/194008

Cited by 48 publications

(45 citation statements)

References 98 publications

(146 reference statements)

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“…For this reason experiments have been performed on many different high-Z ionic species such as U 91+ [11]. However, the required (very) short wavelengths for excitation, such as hard x-rays, makes it very difficult to perform absolute frequency measurements (see e.g., [26] and references therein).…”

Section: Introductionmentioning

confidence: 99%

XUV frequency-comb metrology on the ground state of helium

et al. 2011

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The operation of a frequency comb at extreme ultraviolet (xuv) wavelengths based on pairwise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency-comb laser in the near-infrared range is reported. It is experimentally demonstrated that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p 1 P 1 states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited-state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium atom as a precision phase ruler, yields an estimated timing jitter between the two upconverted-comb laser pulses of 50 attoseconds, which is equivalent to a phase jitter of 0.38 (6) cycles in the xuv at 51 nm. This sets a quantitative figure of merit for the operation of the xuv comb and indicates that extension to even shorter wavelengths should be feasible. The helium metrology investigation results in transition frequencies of 5 740 806 993 (10) and 5 814 248 672 (6) MHz for excitation of the 1s4p and 1s5p 1 P 1 states, respectively. This constitutes an important frequency measurement in the xuv, attaining high accuracy in this windowless part of the electromagnetic spectrum. From the measured transition frequencies an eight-fold-improved 4 He ionization energy of 5 945 204 212 (6) MHz is derived. Also, a new value for the 4 He ground-state Lamb shift is found of 41 247 (6) MHz. This experimental value is in agreement with recent theoretical calculations up to order mα 6 and m 2 /Mα 5 , but with a six-times-higher precision, therewith providing a stringent test of quantum electrodynamics in bound two-electron systems.

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Section: Introductionmentioning

confidence: 99%

XUV frequency-comb metrology on the ground state of helium

et al. 2011

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“…Together with a measurement of the relative oscillator strength of the fluorescence, this allows us to obtain absolute values for the decay rates. We employ the now wellestablished combination of the transportable FLASH-EBIT with an intense x-ray source [25,[27][28][29][30][31] and monitor the charge-state distribution to detect photoionization.…”

Section: Experimental Methodsmentioning

confidence: 99%

Absolute measurement of radiative and Auger rates ofK−shell−vacancystates in highly charged Fe ions

Steinbrügge

Bernitt

Epp³

et al. 2015

Phys. Rev. A

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We present absolute measurements of radiative and Auger decay rates of K-shell vacancies in highly charged iron ions. The ions were resonantly excited with monochromatic x rays from the PETRA III synchrotron source. By measuring x-ray fluorescence and Auger decay simultaneously, absolute transition rates could be determined independently of most experimental parameters. The results confirm theoretical calculations, which are essential to model the photoexcited plasmas in x-ray binary stars and active galactic nuclei.

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“…In the vacuum ultraviolet (VUV), extreme ultraviolet (EUV), or X-ray range, however, there now are tunable light sources that can fill this role. The Heidelberg device FLASH-EBIT has been transported to the synchrotron light sources PETRA (at DESY Hamburg) [37] and BESSY-II (Berlin) [38], and to the free-electron lasers FLASH (at DESY Hamburg) [39,40] and LCLS (at SLAC, Menlo Park, CA) [41]. The electron beam ion trap was used to provide a target of highly charged ions of a known element and predictable highest charge state, and the narrowband VUV/EUV/X-ray radiation was scanned across a spectral band, resulting in detectable fluorescence only when in resonance with atomic transitions (usually ground state transitions) in the target.…”

Section: Active Interrogationmentioning

confidence: 99%

Guest Editor’s Notes on the “Atoms” Special Issue on “Perspectives of Atomic Physics with Trapped Highly Charged Ions”

Trabert

2016

Atoms

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Abstract:The study of highly charged ions (HCI) was pursued first at Uppsala (Sweden), by Edlén and Tyrén in the 1930s. Their work led to the recognition that the solar corona is populated by such ions, an insight which forced massive paradigm changes in solar physics. Plasmas aiming at controlled fusion in the laboratory, laser-produced plasmas, foil-excited swift ion beams, and electron beam ion traps have all pushed the envelope in the production of HCI. However, while there are competitive aspects in the race for higher ion charge states, the real interest lies in the very many physics topics that can be studied in these ions. Out of this rich field, the Special Issue concentrates on atomic physics studies that investigate highly charged ions produced, maintained, and/or manipulated in ion traps. There have been excellent achievements in the field in the past, and including fairly recent work, they have been described by their authors at conferences and in the appropriate journals. The present article attempts an overview over current lines of development, some of which are expanded upon in this Special Issue.

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X-ray laser spectroscopy of highly charged ions at FLASH

Cited by 48 publications

References 98 publications

XUV frequency-comb metrology on the ground state of helium

XUV frequency-comb metrology on the ground state of helium

Absolute measurement of radiative and Auger rates ofK−shell−vacancystates in highly charged Fe ions

Guest Editor’s Notes on the “Atoms” Special Issue on “Perspectives of Atomic Physics with Trapped Highly Charged Ions”

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