Multiple Ionization of Rare Gas Atoms Irradiated with Intense VUV Radiation

Wabnitz, H.; Castro, Alonso; Gürtler, P.; Laarmann, Tim; Laasch, W.; Schulz, Joachim; Möller, Thomas

doi:10.1103/physrevlett.94.023001

Cited by 116 publications

(101 citation statements)

References 19 publications

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“…Wabnitz et al used intensities of ∼ 10 13 W cm −2 at a photon energy of ∼12.7 eV and observed multiple charged ions up to Xe 6+ by multiphoton sequential ionization [8]. By using a description in terms of rate equations, which take into account the simulated FEL pulses and multiphoton cross-sections, Santra et al [9] were able to understand the high degree of ionization compared to ionization in the infrared domain.…”

Section: Introductionmentioning

confidence: 99%

Velocity map imaging of atomic and molecular processes at the free electron laser in Hamburg (FLASH)

Johnsson

Siu

Gijsbertsen

et al. 2008

Journal of Modern Optics

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Velocity map imaging was implemented at the free electron laser in Hamburg to image atomic and molecular photoionization processes at a photon energy of 45.55 eV. High quality momentum distributions were recorded for a range of rare gases (He, Ne, Ar, Kr and Xe) and small molecules (H2, D2, O2, N2, CO2). This proof-of-principle experiment illustrates the potential for using velocity map imaging in order to study non-linear ionization and/or dissociation processes.

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Section: Introductionmentioning

confidence: 99%

Velocity map imaging of atomic and molecular processes at the free electron laser in Hamburg (FLASH)

Johnsson

Siu

Gijsbertsen

et al. 2008

Journal of Modern Optics

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“…A recent comparison between experiment and theory showed perfect agreement [16]. On the other hand, multiphoton ionization of rare gas atoms in the regime of high photon energies, arXiv:0806.4501v1 [physics.atom-ph] 27 Jun 2008 which allows for direct ionization of one electron by a single photon, has been investigated at the free electron laser (FEL) facility at DESY in Hamburg which gave the first experimental evidence of a multi-photon process in the high photon energy regime [17,18]. Up to now, there still exist discrepancies between theory and experiment [19] which may also be attributed to still limited experimental work in the field since the high-intensity VUV and XUV sources are presently under construction.…”

Section: Introductionmentioning

confidence: 99%

Angular distributions of atomic photoelectrons produced in the uv and xuv regimes

Bauch

Bönitz

2008

Phys. Rev. A

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We present angular distributions of photoelectrons of atomic model systems excited by intense linearly polarized laser pulses in the VUV-and XUV-regime. We solve the multi-dimensional timedependent Schrödinger equation for one particle on large spatial grids and investigate the direction dependence of the ionized electrons for isotropic s-states as well as p-states. Although the ponderomotive potential is small compared to the binding energy of the initially bound electron and the photon energy of the exciting laser field, richly structured photoelectron angular distributions are found which sensitively depend on the laser frequency and intensity as well as on the number of absorbed photons. The occuring shapes are explained in terms of scattering mechanisms.

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“…When focused into a spot of a few micrometers in diameter, the radiation can reach peak irradiance levels of more than 10 13 W cm −2 where nonlinear effects such as atomic multiphoton ionization occur. [3][4][5][6] A key point for the understanding and theoretical description of nonlinear processes is, in general, their dependence on irradiance. Therefore, among other quantities such as pulse energy and duration, spot-size determination of focused high-intensity VUV and XUV radiation is mandatory.…”

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confidence: 99%

Method based on atomic photoionization for spot-size measurement on focused soft x-ray free-electron laser beams

Sorokin

Gottwald

Hoehl

et al. 2006

Applied Physics Letters

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A method has been developed and applied to measure the beam waist and spot size of a focused soft x-ray beam at the free-electron laser FLASH of the Deutsches Elektronen-Synchrotron in Hamburg. The method is based on a saturation effect upon atomic photoionization and represents an indestructible tool for the characterization of powerful beams of ionizing electromagnetic radiation. At the microfocus beamline BL2 at FLASH, a full width at half maximum focus diameter of ͑15± 2͒ m was determined. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2397561͔ Recent progress in developing pulsed high-power vacuum ultraviolet ͑VUV͒ and soft x-ray uv ͑XUV͒ sources, such as higher-harmonic generation ͑HHG͒ sources 1 and free-electron lasers ͑FELs͒, 2 has opened the door to extended research on nonlinear interaction of electromagnetic radiation with matter from the optical region to shorter wavelengths. When focused into a spot of a few micrometers in diameter, the radiation can reach peak irradiance levels of more than 10 13 W cm −2 where nonlinear effects such as atomic multiphoton ionization occur. 3-6 A key point for the understanding and theoretical description of nonlinear processes is, in general, their dependence on irradiance. Therefore, among other quantities such as pulse energy and duration, spot-size determination of focused high-intensity VUV and XUV radiation is mandatory.Recently, two conventional methods have been applied to measure the spot size of focused HHG beams, namely, the knife-edge 7 and the fluorescence screen technique. 1,[8][9][10] Both methods provide information on two-dimensional photon intensity distribution with a spatial resolution of 1 to 2 m. The possibility of applying these techniques to FELs is, however, limited. The FEL pulse energy levels of VUV and XUV radiation may be some orders of magnitude higher than those of HHG sources and can cause radiation damage on fluorescence screens and, in general, on any solid irradiated surface. Moreover, due to its statistical nature, a beam of FEL radiation based on self-amplified spontaneous emission 2 may strongly fluctuate from shot to shot, perpendicular to the propagation axis, and requires spot-size measurements which do not depend on the beam position. In this context, we describe a method which has been used to determine the beam waist and spot size of a focused beam at the XUV-FEL facility FLASH of the Deutsches Elektronen-Synchrotron in Hamburg. 11 It is based on a saturation effect upon photoionization of a rare gas and manifests itself by a sublinear increase in the ion yield as a function of the photon number per pulse. It is due to a considerable reduction in the number of target atoms within the interaction zone by ionization with a single photon pulse and becomes stronger with decreasing beam cross section. The method is indestructible and not affected by fluctuations of the beam position. Moreover, it can easily be realized in any ionization chamber by introducing a ͑rare͒ gas and detecting the photoionization signal as a fun...

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Multiple Ionization of Rare Gas Atoms Irradiated with Intense VUV Radiation

Cited by 116 publications

References 19 publications

Velocity map imaging of atomic and molecular processes at the free electron laser in Hamburg (FLASH)

Velocity map imaging of atomic and molecular processes at the free electron laser in Hamburg (FLASH)

Angular distributions of atomic photoelectrons produced in the uv and xuv regimes

Method based on atomic photoionization for spot-size measurement on focused soft x-ray free-electron laser beams

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