Nonperturbative quantum electrodynamics theory of high-order harmonic generation

Gao, Lianghui; Li, Xiaofeng; Fu, Panming; Freeman, R. R.; Guo, Dong‐Sheng

doi:10.1103/physreva.61.063407

Cited by 59 publications

(40 citation statements)

References 22 publications

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“…According to the nonperturbative quantum scattering theory of HHG [25], an initially bound electron is excited into a Volkov state under the action of the intense laser field. The electron in the Volkov state may recombine with its parent core, accompanied by the emission of a harmonic photon to get rid of the redundant energy absorbed from the laser field.…”

Section: High-order Harmonic Generation Rate Formula For Moleculesmentioning

confidence: 99%

“…In the framework of this theory, Gao et al [25] derived a quantum scattering theory of HHG. In this treatment, an analytical expression of the harmonic generation is obtained by treating the state of the quasifree electron in the laser field as a Volkov state.…”

Section: Introductionmentioning

confidence: 99%

“…II, following Gao et al's [25] treatment and using the LCAO theory, we derive the HHG rate formula for molecules. In Sec.…”

Section: Introductionmentioning

confidence: 99%

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Intensity-dependent interference effect in high-order harmonic generation from alignedH2 +molecules

Zhang

et al. 2011

Phys. Rev. A

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Based on the nonperturbative quantum scattering theory of high-order harmonic generation (HHG) and using the linear combination of atomic orbitals theory of molecular orbitals, we derive the HHG rate formula for molecules. Employing the formula, we study the intensity dependence of the interference effect induced by the molecular structure. We find that the molecular HHG was modulated by the interference not only in the recombination process but also in the ionization process. The location of the interference minimum in HHG shifts to higher energy by a quantity of the ponderomotive energy as the laser intensity increases.

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Section: High-order Harmonic Generation Rate Formula For Moleculesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intensity-dependent interference effect in high-order harmonic generation from alignedH2 +molecules

Zhang

et al. 2011

Phys. Rev. A

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“…It is not our intent to discuss the pros and cons of each model and therefore refer the interested reader to three excellent review articles [6][7][8][9] where they compare, contrast, and consider the advantages and disadvantages of each approach. The most recent quantum field model appears in [10][11][12][13] and contain adequate references to earlier works. However, by their very nature many of these models are very complicated and computer intensive and although they provide insight and explanations for the purely quantum effects they lose the simplicity characteristic of the semiclassical model.…”

Section: Introductionmentioning

confidence: 99%

Contribution of Bound States to the Harmonic Generation in Hydrogen at Moderate Laser Intensities

Davis¹,

Bláha²

2002

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“…In the recent two decades, many observations of odd-only harmonics accompanying ATI peaks have been reported [1,2]. Almost all related theoretical models are based on an assumption that electrons which emit the odd-only harmonics transit back to the initial bound states [3][4][5][6][7][8][9] and are, therefore, called recombination models. Electromagnetic processes conserve charge, parity, and time reversions.…”

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confidence: 99%

Even-odd harmonics generated from above-threshold ionization

et al. 2013

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We are reporting a theoretical prediction: The photoelectrons forming above-threshold-ionization (ATI) peaks emit both even and odd harmonics. These harmonics exhibit plateau and cut-off features similar to those odd-only harmonics observed in ATI experiments.Keywords strong-field laser physics, above-threshold inoization, high harmonic generation, evenodd harmonics, nonperturbative quantum electrodynamics PACS numbers 32.80.Rm, 42.65.Ky, 12.20.Ds, 03.65.Nk High harmonic generation (HHG) accompanying abovethreshold ionization (ATI) is one of the most interesting phenomena in strong-field laser physics. In the recent two decades, many observations of odd-only harmonics accompanying ATI peaks have been reported [1,2]. Almost all related theoretical models are based on an assumption that electrons which emit the odd-only harmonics transit back to the initial bound states [3][4][5][6][7][8][9] and are, therefore, called recombination models. Electromagnetic processes conserve charge, parity, and time reversions. The cancelation of even harmonics in theoretical derivations of recombination models is due to the symmetry of initial and final boundary conditions in the sub-Hilbert space of electron, as a natural consequence of the parity conservation or the charge-parity conservation. This success of recombination models really indicates that the electrons emitting odd-only harmonics are not the photoelectrons forming ATI peaks, but those transiting back to the initial state with no contributions to ATI peaks. When more ionized electrons transit back to the initial bound state, the ATI rate should reduce and show stability [10]. Thus, the odd-only HHG is not really accompanying the ATI peaks, rather accompanying the stabilization of atoms in ATI. Then, a natural question is: What kind of harmonics will electrons emit if they do not transit back to the initial state, especially the photoelectrons forming ATI peaks?Previous theoretical studies proved that the photoelectrons forming ATI peaks had spontaneous emission, enforced by the energy-momentum conservation, and the frequencies of the spontaneous emission were spaced by one laser photon energy [11]. With the asymmetric boundary condition, the harmonics emitted by photoelectrons forming the ATI peaks must show both even and odd orders. Actually, there was already this type of high harmonic spectra observed from plasmas generated by laser light [12][13][14] and received some attention [15][16][17][18][19]. A question is: why ATI experiments do not show the even-odd harmonics? While, this question should not prohibit a theoretical prediction that photoelectrons forming ATI peaks emit both even and odd harmonics. Further studies on the spectra of these harmonics are necessary to facilitate further experimental observations. In 1991, Kulander et al. [20], in a computer simulation of a three-dimensional hydrogen model, showed evidence of even harmonics. They, using parity conservation, interpreted the evidence as a result of the asymmetry of the electric field. In 1992, ...

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Nonperturbative quantum electrodynamics theory of high-order harmonic generation

Cited by 59 publications

References 22 publications

Intensity-dependent interference effect in high-order harmonic generation from alignedH2 +molecules

Intensity-dependent interference effect in high-order harmonic generation from alignedH2 +molecules

Contribution of Bound States to the Harmonic Generation in Hydrogen at Moderate Laser Intensities

Even-odd harmonics generated from above-threshold ionization

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