Many-Electron Dynamics of a Xe Atom in Strong and Superstrong Laser Fields

Yamakawa, Koichi; Akahane, Y.; Fukuda, Yuji; Aoyama, M.; Inoue, Norihiro; Ueda, Hitoshi; Utsumi, Takayuki

doi:10.1103/physrevlett.92.123001

Cited by 71 publications

(36 citation statements)

References 25 publications

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“…The most likely reason is that simultaneous multiphoton transitions are involved whose rates increase, according to Eq. (1), with shorter pulse duration τ at constant radiant exposure H. The transition energy from Xe 7þ to Xe 8þ amounts to more than 100 eV [43] and, thus, exceeds our photon energy of 93 eV so that at least two simultaneous photoabsorptions are required.…”

Section: Prl 112 213002 (2014) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 89%

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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Section: Prl 112 213002 (2014) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 89%

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

et al. 2014

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“…As mentioned earlier in the text these are predictions of the theory which should be compared with experimental results, if any (in [10] the similar procedure for linearly polarized field is strongly confirmed by the experiment). That could clarify the mechanisms of the tunnel ionization of atoms in low frequency laser fields.…”

Section: Final Remarksmentioning

confidence: 99%

“…we, as is done in experiments [10] and also analyzed in [9], define and calculate the change of ionization energy for each ejected electron. So graphs shown are depending on various η [1,300], and on field intensities I = 10 12 -10 17 W/cm 2 , which are fixed for each separate graph.…”

Section: Calculating the Transition Rates For Circularlymentioning

confidence: 99%

“…Therefore there is much less photons which could increase the momentum of ejected electrons, which can be seen from the lesser difference between corresponding curves. This is a prediction that should be tested experimentally, of course (for the linear polarization see [10]). …”

Section: Calculating the Transition Rates For Circularlymentioning

confidence: 99%

“…It is definitely shown [1][2][3][4][5][6][7][8][9][10] that for low frequency laser fields one of the mostly used models is based on the tunneling regime: external field, due to its long duration, leads to the formation of the barrier through which electron can tunnel out. Among theories using this model the ADK-theory [1] is widely recognized.…”

Section: Introductionmentioning

confidence: 99%

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Circularly Polarized Laser Fields, with Different Z, Including Non-Zero Initial Momentum

2011

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In this paper, by estimating the influence of different atom charge Z to the transition rate in tunnel ionization of atoms in strong laser fields we are devoloping further the observations from our earlier work. That is in the process of tunnel ionization including non-zero momentum into calculation of the transition rate gives result in lower transition rates for ejecting electrons from atoms by low-frequency laser fields, indicating that much of the photons are engaged in transferring energy to the free electron and thus unable to contribute to the effect of ionization. This is a conclusion that needs further experimental testing, which would clarify the mechanisms of tunnel ionization.

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