Above-threshold ionization with subpicosecond laser pulses

Freeman, R. R.; Bucksbaum, P. H.; Milchberg, H. M.; Darack, S.; Schumacher, Douglass; Geusic, M. E.

doi:10.1103/physrevlett.59.1092

Cited by 808 publications

(443 citation statements)

References 18 publications

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“…For single ionization the coincident electron-momentum distributions [ Fig. 1(a)] are quite similar at both intensities, clearly exhibiting a series of low-order ATI peaks, induced by so-called Freeman resonances [19]. They are discussed in some detail in [13] but are not the focus of this Letter.…”

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confidence: 94%

Strong-Field Double Ionization of Ar below the Recollision Threshold

et al. 2008

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Nonsequential double ionization of Ar by 45 fs laser pulses (800 nm) at 4-7 10 13 W=cm 2 was explored in fully differential measurements. Well below the field-modified recollision threshold we enter the multiphoton regime. Strongly correlated back-to-back emission of the electrons along the polarization direction is observed to dominate in striking contrast to all previous data. No effect of Coulomb repulsion can be found, the predicted cutoff in the sum-energy spectra of two emitted electrons is confirmed, and the potential importance of multiple recollisions is discussed. DOI: 10.1103/PhysRevLett.101.053001 PACS numbers: 32.80.Rm, 31.90.+s, 32.80.Fb, 32.80.Wr Within the past three decades extensive studies on the interaction of intense laser fields with atoms and molecules have resulted in a profound understanding of various strong-field phenomena. Prominent examples are abovethreshold ionization (ATI) [1] or high-order harmonic generation [2], both essentially treatable within the single active electron (SAE) approximation. Correlated fewelectron processes, on the other hand, most important, for example, in nonsequential double (multiple) ionization (NSDI) (for a recent review see, e.g., [3]) have, until the present day, resisted any comprehensive modeling.Recently, however, a breakthrough was achieved at high intensities ( PW=cm 2 ) [4]. The application of many-particle imaging techniques [reaction microscopes and cold target recoil ion momentum spectroscopy (COLTRIMS)] [5] has allowed recording (multi)differential data on strong-field few-electron reactions and sophisticated calculations (see, e.g., [6] and references therein) have advanced their theoretical interpretation. As a result, a commonly accepted though simple picture has emerged, characterizing NSDI. Here an electron first tunnels into the field, is then accelerated, and finally thrown back onto its parent ion by the oscillating laser field. During ''recollision'' n-fold ionization might occur either in a direct e; ne -like encounter or indirectly via recollision-induced excitation of the ion plus subsequent field ionization (RESI) [7]. Signatures of the former are that both electrons are exclusively emitted into the same hemisphere along the polarization direction leading to ''double-hump'' shaped parallel momentum distributions of the ions (compensating the electron momenta). For RESI instead, according to the present understanding, the electrons can be emitted either parallel or back to back, thus filling the valley in between the double hump for the ions. Beyond the well-accepted simple scenario, however, major questions about the correlated electron emission are still far from being understood and are extensively investigated [6,8] because recollision is at the very heart of attoscience, molecular tomography, or imaging [9].At low intensities one intriguing though still widely unexplored question did arise early on within the above picture [10]. What happens when the energy of the recolliding electron of up to 3:17U P is not sufficient t...

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confidence: 94%

Strong-Field Double Ionization of Ar below the Recollision Threshold

et al. 2008

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“…This equation is the modified Einstein relation for the photoelectric effect and completely equivalent to the one originally given by Freeman et al [2].…”

Section: Using the Data Table To Calculate Freeman Resonancesmentioning

confidence: 98%

“…To show how to use the data table in calculations of real physical processes, we apply our method to the treatment of Freeman resonances [2]. We choose a xenon atom driven by laser light of 616 nm wavelength as the sample atom.…”

Section: Using the Data Table To Calculate Freeman Resonancesmentioning

confidence: 99%

“…After the invention of the laser, many new important physical phenomena were observed, such as above-threshold ionization [1], Freeman resonances [2][3][4][5][6][7], high-order harmonic generation [8,9], etc. At the beginning of the last century, Einstein proposed a two-level model [10] to study the transitions between energy levels of an atom that interacts with light.…”

Section: Introductionmentioning

confidence: 99%

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Precise calculation of quasienergies of a driven two-level atom based on the Guo–Wu–Van Woerkom solution

Wang

Zhang

et al. 2010

Atomic Data and Nuclear Data Tables

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“…In 1987, R. R. Freeman et al found experimentally [11] that the above-threshold ionization (ATI) peaks broke up into many small peaks when the laser pulses were short. Such multiphoton resonances have been observed for years and modelled theoretically using Floquet and numerical approaches [12].…”

Section: Introductionmentioning

confidence: 99%

Algebraic solution for a two-level atom in radiation fields and the Freeman resonances

Guo

Woerkom

2006

Phys. Rev. A

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Using techniques of complex analysis in an algebraic approach, we solve the wave equation for a two-level atom interacting with a monochromatic light field exactly. A closed-form expression for the quasi-energies is obtained, which shows that the Bloch-Siegert shift is always finite, regardless of whether the original or the shifted level spacing is an integral multiple of the driving frequency, ω. We also find that the wave functions, though finite when the original level spacing is an integral multiple of ω, become divergent when the intensity-dependent shifted energy spacing is an integral multiple of the photon energy. This result provides, for the first time in the literature, an ab-initio theoretical explanation for the occurrence of the Freeman resonances observed in above-threshold ionization experiments. PACS number(s): 32.80. Rm, 42.65.Ky, 12.20Ds, 03.65.Nk

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Above-threshold ionization with subpicosecond laser pulses

Cited by 808 publications

References 18 publications

Strong-Field Double Ionization of Ar below the Recollision Threshold

Strong-Field Double Ionization of Ar below the Recollision Threshold

Precise calculation of quasienergies of a driven two-level atom based on the Guo–Wu–Van Woerkom solution

Algebraic solution for a two-level atom in radiation fields and the Freeman resonances

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