Attosecond Resolved Charging of Ions in a Rare-Gas Cluster

Georgescu, Ionuţ; Saalmann, Ulf; Rost, Jan M.

doi:10.1103/physrevlett.99.183002

Cited by 18 publications

(29 citation statements)

References 18 publications

(28 reference statements)

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“…The extreme ultraviolet (XUV) regime offers unique opportunities in the study of the dynamics of finite systems such as clusters [22,23]. Single photon ionization from the ground state of rare-gas atoms is accessible, though inner-shell ionization is not.…”

Section: Introductionmentioning

confidence: 99%

Clusters in intense XUV pulses: Effects of cluster size on expansion dynamics and ionization

et al. 2011

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We examine the effect of cluster size on the interaction of Ar 55 -Ar 2057 with intense extreme ultraviolet (XUV) pulses, using a model we developed earlier that includes ionization via collisional excitation as an intermediate step. We find that the dynamics of these irradiated clusters is dominated by collisions. Larger clusters are more highly collisional, produce higher charge states, and do so more rapidly than smaller clusters. Higher charge states produced via collisions are found to reduce the overall photon absorption, since charge states of Ar 2+ and higher are no longer photoaccessible. We call this mechanism collisionally reduced photoabsorption, and it decreases the effective cluster photoabsorption cross section by more than 30% for Ar 55 and 45% for Ar 2057 . The time evolution of the electron kinetic energy distribution begins as a (mostly) Maxwellian distribution. Further, the electron velocity distribution of large clusters quickly become isotropic while smaller clusters retain the inherent anisotropy created by photoionization. Last, the total electron kinetic-energy distribution is integrated over the spatial profile of the laser and the log-normal distribution of cluster size for comparison with a recent experiment [C. Bostedt et al., Phys. Rev. Lett. 100, 133401 (2008)], and good agreement is found.

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Section: Introductionmentioning

confidence: 99%

Clusters in intense XUV pulses: Effects of cluster size on expansion dynamics and ionization

et al. 2011

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“…Common methods to study clusters in intense short wavelength pulses are electron and ion spectroscopy [43,64,65,66,67], uorescence spectroscopy [68] and elastic scattering [10,53,69,70]. Also many theoretical studies have been performed on this subject [40,41,71,72,73,74]. However many processes during and after the ionization are not yet well understood and are still under active investigation.…”

Section: Chaptermentioning

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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“…Alternatively, one may use a longer pump pulse, that is, hundreds of femtoseconds in duration, and apply the attosecond probe pulse during the pump pulse. This scenario allows one to map out the time-dependent charging of the cluster caused by the pump pulse before Coulomb explosion sets in during which recombination of electrons will reduce the ion charges [51]. Such recombination processes are yet another transient phenomenon, difficult to detect without attosecond pulse techniques.…”

Section: Creating and Probing A Dense Non-equilibrium Nano-plasma By mentioning

confidence: 99%

Ultrafast Dynamics in Extended Systems

Saalmann

Rost

2014

Attosecond Nanophysics

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Attosecond Resolved Charging of Ions in a Rare-Gas Cluster

Cited by 18 publications

References 18 publications

Clusters in intense XUV pulses: Effects of cluster size on expansion dynamics and ionization

Clusters in intense XUV pulses: Effects of cluster size on expansion dynamics and ionization

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

Ultrafast Dynamics in Extended Systems

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