�ber die Entstehung der ?-Strahl-Spektren radioaktiver Substanzen

Meitner, Lise

doi:10.1007/bf01326962

Cited by 111 publications

(52 citation statements)

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“…As a result of the photoionization process, the atomic Coulomb potential is recongured and other electrons can end up above the ionization potential in bound states (shake-up) or in the continuum (shake-o). [60,61] the hole is lled with an electron from a higher lying shell. The released energy is transferred to another electron from that shell or a higher shell that is ejected.…”

Section: Figure 211mentioning

confidence: 99%

Size-Dependent Ultrafast Ionization Dynamics of Nanoscale Samples in Intense Femtosecond X-Ray Free-Electron-Laser Pulses

et al. 2012

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All matter exposed to intense femtosecond x-ray pulses from the Linac Coherent Light Source (LCLS) free-electron laser is strongly ionized on femtosecond time scales. On these time scales, the ionization is competing with the lifetimes of the created inner-shell vacancies. In the present work, it is shown that for nanoscale objects the environment, i.e., nanoparticle size, is an important parameter for the time-dependent ionization dynamics in intense x-ray pulses because it has an in uence on the inner-shell vacancy liftimes. As a sample system, argon atoms and clusters with sizes between ⟨N⟩ = 55 and ⟨N⟩ = 1600 were chosen. The clusters were irradiated with 480 eV x-ray pulses reaching power-densities of up to a few 10 17 W/cm 2 . At this photon energy dominantly the argon L-shell is ionized and the remaining vacancies are most likely lled via Auger decay. To investigate the electron dynamics, the x-ray pulse length was tuned between 30 fs and 85 fs, using the novel LCLS slotted spoiler technique. The ionization products were measured with an ion time-of-ight spectrometer with a special slit aperture. This aperture e ciently suppresses atomic background, which yields cluster spectra of unprecedented quality. Spectra for di erent pulse lengths and a range of pulse energies were collected for atoms and all cluster sizes. In atoms, as in clusters, longer x-ray pulses are absorbed more e ciently than shorter x-ray pulses with the same number of photons. To shed light on size-dependent e ects in clusters, an independent measure for the time-dependent component of the absorption for every cluster size was found by means of x-ray induced transparency increase (XITI). The XITI increases from atoms to clusters and shows a clear cluster size dependence. A rate equation model for the ionization of atomic systems has been developed to support the interpretation of the experimentally determined XITI as a function of the cluster size. As a result, the Auger lifetimes of large argon clusters are found to be longer than for small clusters and isolated atoms. This is due to delocalization of the valence electrons in the x-ray induced nanoplasma, resulting in a smaller overlap between valence electrons and core holes. As a consequence, large nanometer sized samples absorb intense femtosecond x-ray pulses less e ciently than small ones.

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Section: Figure 211mentioning

confidence: 99%

Size-Dependent Ultrafast Ionization Dynamics of Nanoscale Samples in Intense Femtosecond X-Ray Free-Electron-Laser Pulses

et al. 2012

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“…The momentum is given by the analytical expression Equation 4.5b which contains a constant drift momentum and an oscillatory quiver momentum. 1) 1) Note that the graph shows p(z) not p(t), which is why the frequencies after the collision (z ≳ 2) appear to be different despite they are the same in both cases. During a collision the drift momentum does not stay constant necessarily.…”

Section: Extended Systems and Optical Swingbysmentioning

confidence: 99%

Ultrafast Dynamics in Extended Systems

Saalmann

Rost

2014

Attosecond Nanophysics

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“…It is in principle applicable to all elements of the periodic system with the exception of the first two: hydrogen (H) and helium (He), thereby covering an energy region from about 50 eV to 100 keV [32].…”

Section: X-ray Fluorescence (Xrf) Spectroscopymentioning

confidence: 99%