Absolute cross sections for the photoionization of 4d electrons in Xe<sup>+</sup>and Xe<sup>2+</sup>ions

Andersen, Per; Andersen, T.; Folkmann, F.; Ivanov, V. K.; Kjeldsen, H.; West, John B.

doi:10.1088/0953-4075/34/10/314

Cited by 68 publications

(71 citation statements)

References 23 publications

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“…transitions, respectively, in agreement with literature values [15] (nl −1 j symbolizes a hole in the nl orbital with angular momentum j; the corresponding term symbol is given in parentheses). The ratio of the areas of the two fine-structure absorption lines, defined as R = I 3/2→5/2 /I 1/2→3/2 , is found to be R = 6.5 ± 1.1.…”

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confidence: 90%

Quantum State-Resolved Probing of Strong-Field-Ionized Xenon Atoms Using Femtosecond High-Order Harmonic Transient Absorption Spectroscopy

et al. 2007

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Femtosecond high-order harmonic transient absorption spectroscopy is used to resolve the complete |j, m quantum state distribution of Xe + produced by optical strong-field ionization of Xe atoms at 800 nm. Probing at the Xe N 4/5 edge yields a population distribution ρ j,|m| of ρ 3/2,1/2 : ρ 1/2,1/2 : ρ 3/2,3/2 = 75 ± 6 : 12 ± 3 : 13 ± 6%. The result is compared to a tunnel ionization calculation with the inclusion of spin-orbit coupling, revealing nonadiabatic ionization behavior. The sub-50-fs time resolution paves the way for table-top extreme ultraviolet absorption probing of ultrafast dynamics.PACS numbers: 42.50. Hz, 32.80.Rm, 42.65.Ky, Studies of laser-atom interactions in the nonperturbative, strong-field regime elucidate novel phenomena such as above-threshold ionization [1,2], nonsequential double ionization [3], and high-order harmonic generation [4,5,6]. While these processes are extensively studied both experimentally and theoretically, details remain unknown about the |j, m state distribution of the photoion produced by the initial photoionization step (m is the projection quantum number associated with the total angular momentum j of the hole). Moreover, experimental tests of theoretical models for strong-field ionization mostly rely on measuring the ion yield as a function of laser peak intensity [7]. The strong dependence of ionization yields on the orbital angular momentum and its direction relative to the laser polarization axis, as predicted by most theoretical models (e.g., the Ammosov-Delone Krainov (ADK) rates [8]), suggests that knowledge of the complete |j, m state distribution can be used as an additional benchmark for theory. Young et al. recently reported the use of synchrotron x-ray pulses to probe the hole-orbital alignment of Kr + photoions generated in the strong-field ionization of Kr [9]. The unresolved finestructure transitions prevented retrieval of the complete |j, m state distribution. However, the observed degree of alignment is reproduced by the |j, m state distribution obtained by tunnel ionization calculations with the inclusion of spin-orbit coupling [10].Here we investigate the experimental and theoretical strong-field ionization of xenon to extract the complete |j, m quantum state distribution. Femtosecond extreme ultraviolet (EUV) transient absorption spectroscopy is demonstrated with a laser-based, high-order harmonic probe source for the experiments; results are compared to tunnel ionization calculations that incorporate spinorbit coupling. The resultant angular momentum distribution and hole-orbital alignment of the Xe + photoions are measured by probing the transition from the 4d core level to the 5p valence shell. These measurements allow the determination of the complete |j, m quantum state distribution, which is compared to theory.The schematic of the experimental setup is illustrated in Fig. 1. Briefly, the amplified output from a commercial Ti:sapphire laser system (2.4 W, 800 nm, 45 fs, 1 kHz) is sent to a 20 : 80 beamsplitter to produce the optical pump an...

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Quantum State-Resolved Probing of Strong-Field-Ionized Xenon Atoms Using Femtosecond High-Order Harmonic Transient Absorption Spectroscopy

et al. 2007

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“…The reason might be the 4d inner-shell giant resonance which dominates the photoionization of Xe at 93 eV and leads to excited states with lifetimes of a few femtoseconds, decaying via Auger effect to higher charge states [36][37][38]. Similar mechanisms hold for the photoionization of Xe þ to Xe 6þ as the first steps of a sequential ionization scheme [39,40]. As a consequence, the 4d vacancy is frequently refilled for further excitation.…”

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Time-Dependent Multiphoton Ionization of Xenon in the Soft-X-Ray Regime

et al. 2014

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The time-dependent multiphoton ionization of xenon atoms is studied with femtosecond pulses in the excitation range of the 4d giant resonance at the photon energy of 93 eV. Benefiting from a new operation mode of the free electron laser FLASH, the measurements are performed with varying pulse durations. A strong dependence of the ion charge distribution on the pulse duration allows the different multiphoton mechanisms behind the multiple photoionization of xenon to be disentangled up to a charge state of Xe 10þ . The results up to Xe 8þ are well explained by sequences of single photon, multiphoton, and Auger processes, but higher charge state generation suggests the need for collective electron multiphoton excitations. DOI: 10.1103/PhysRevLett.112.213002 PACS numbers: 32.80.Rm, 32.80.Fb, 41.60.Cr, 42.50.Hz The highly intense and ultrashort radiation pulses of the new free electron laser (FEL) facilities in Europe [1,2], the United States [3], and Japan [4,5] can significantly extend the study of interaction of x rays with matter to the nonlinear regime of multiphoton processes. A number of fascinating FEL experiments of multiphoton ionization have already been carried out on solids, clusters, molecules, and on free atoms [[6,7,8,9], and references therein]. Whereas in the regime of optical femtosecond lasers, simultaneous multiphoton, above-threshold, and strongfield ionization are the mechanisms of relevance [10,11], the nonlinear interaction of soft and hard x rays with atoms at photon energies above the first ionization threshold has been shown to be dominated by sequential processes in which an excited atom or ion created in a preceding step represents the target for a subsequent step [12][13][14][15][16][17][18][19][20]. For higher ionization charges and ionization thresholds which exceed the photon energy, the mechanisms may be rather complex because simultaneous multiphoton ionization processes come into play for the higher steps of an ionization sequence [12,21].A prime example is the multiphoton multiple ionization of Xe in the vicinity of the so-called 4d giant resonance in the extreme ultraviolet (EUV) between 90 eV and 110 eV photon energy where charge states up to Xe 21þ were observed at irradiance levels in the order of 10 16 W=cm 2[22]. A sequential scheme requires 19 steps and almost 60 EUV photons to generate Xe 21þ from atomic Xe, and more than a single photon is required for each step from Xe 7þ on. The role of the 4d giant resonance and the impact of collective electron excitation on this particular behavior are still-open scientific questions of fundamental importance [22][23][24][25][26]. Since the different multiphoton schemes depend in different ways on the FEL pulse duration, as has recently been summarized [27], photoionization experiments at varying pulse duration may help to disentangle the underlying mechanisms. Experiments at the Linac Coherent Light Source (LCLS) have demonstrated that sequences of inner-shell excitation in the harder x-ray regime and successive refilling via A...

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“…While up to Xe 3+ , most of the integral oscillator strength of the 4d − nf, f transition of about 10 (there are 10 electrons in the 4d shell) contributes to the giant resonance [66], for higher charge states the ratio going into the 4d − 4f resonances increases, also due to the decreasing number of possible excitation channels. [62,63,64,65,66,67]. A transition from a broad continuum-like absorption resonance for neutral xenon and lower charge states to sharp absorption resonances for higher charge states can be observed.…”

Section: Ionization Properties Of Atomic Xenon In the Xuv Rangementioning

confidence: 96%

“…Due to available resonances with high cross-sections, early experiments using radiation from bending magnets were in fact carried out on xenon in the XUV range [62]. In the meanwhile, absolute cross sections for xenon in the XUV range are available up to Xe 7+ [62,63,64,65,66,67]. Atomic and ionic absorption cross sections are displayed in Fig.…”

Section: Ionization Properties Of Atomic Xenon In the Xuv Rangementioning

confidence: 99%

Ionization and Plasma Dynamics of Single Large Xenon Clusters in Superintense XUV Pulses

Rupp

2016

Springer Theses

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In this work fundamental mechanisms of the interaction between matter and strong shortwavelength pulses have been investigated. For the experiments ultrashort and highly intense light pulses in the extreme-ultraviolet spectral regime from the Free-Electron Laser in Hamburg FLASH have been used. They provide access to new fields of experiments such as imaging of single nanometer-sized structures. Rare gas clusters in the gas phase were investigated as ideal model systems for light-matter interaction. From the scattering patterns of individual clusters, their size and shape as well as the power density they were exposed to can be determined. But also light-induced changes in the clusters on a femtosecond time scale are encoded in the scattered light. By combining single cluster imaging with the coincident measurement of ion spectra, it is possible to sort the single shot data based on the information in the scattering patterns. Thus, the averaging of cluster size distributions and FEL power density profiles which has been apparent in virtually all previous studies on rare gas clusters can be overcome. The well-defined conditions in the single shot data sorted for cluster size yield unique insight into the nanoplasma dynamics.Large xenon clusters with diameters of hundreds of nanometers up to microns could be produced and investigated for the first time. Their scattering patterns reveal a complex, hailstone-like structure, yielding new insight into cluster morphology and growth mechanisms. The characteristic energy distributions of the ions determined from the time-of-flight spectra of very large single xenon clusters indicate that only ions from the outermost atomic monolayer of the cluster explode off. At the same time, the highly efficient recombination in the remaining, quasi-neutral nanoplasma allows for most atoms in the cluster to return back to neutral state. From the corresponding scattering patterns intensity profiles can be extracted. Mie theory yields insight into the optical properties of the clusters. In the intensity profiles of large clusters, modulations are observed which indicate the development of a core-shell system within the nanoplasma. The core and a shell that is up to 50 nm thick differ in the optical properties, yielding insight into ultrafast rearrangements of the electronic structure of the cluster.

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Absolute cross sections for the photoionization of 4d electrons in Xe⁺and Xe²⁺ions

Cited by 68 publications

References 23 publications

Quantum State-Resolved Probing of Strong-Field-Ionized Xenon Atoms Using Femtosecond High-Order Harmonic Transient Absorption Spectroscopy

Quantum State-Resolved Probing of Strong-Field-Ionized Xenon Atoms Using Femtosecond High-Order Harmonic Transient Absorption Spectroscopy

Time-Dependent Multiphoton Ionization of Xenon in the Soft-X-Ray Regime

Ionization and Plasma Dynamics of Single Large Xenon Clusters in Superintense XUV Pulses

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Absolute cross sections for the photoionization of 4d electrons in Xe+and Xe2+ions

Cited by 68 publications

References 23 publications

Quantum State-Resolved Probing of Strong-Field-Ionized Xenon Atoms Using Femtosecond High-Order Harmonic Transient Absorption Spectroscopy

Quantum State-Resolved Probing of Strong-Field-Ionized Xenon Atoms Using Femtosecond High-Order Harmonic Transient Absorption Spectroscopy

Time-Dependent Multiphoton Ionization of Xenon in the Soft-X-Ray Regime

Ionization and Plasma Dynamics of Single Large Xenon Clusters in Superintense XUV Pulses

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Absolute cross sections for the photoionization of 4d electrons in Xe⁺and Xe²⁺ions