Molecular orbital dependence of high-order harmonic generation

Marangos, Jonathan P.; Altucci, C.; Velotta, R.; Heesel, E.; Springate, E.; Pascolini, M.; Poletto, Luca; Villoresi, Paolo; Vozzi, C.; Sansone, G.; Anscombe, M.P.; Caumes, Jean-Pascal; Stagira, S.; Nisoli, M.

doi:10.1080/09500340500159641

Cited by 8 publications

(5 citation statements)

References 38 publications

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“…The strong-field approximation (SFA) has been widely used for theoretical simulations of HHG from atoms [22] and molecules [28,29,30,31,32,33,34,35]. This model is known to give qualitatively good results, especially for harmonics near the cutoff.…”

Section: A Methods Of Solving the Time-dependent Schrödinger Equationmentioning

confidence: 99%

“…For molecules, accurate numerical solution of the TDSE is much more computational demanding and has not been carried out except for the simplest molecules such as H + 2 [12,26,27]. Thus most of the existing calculations for HHG from molecules were performed using the SFA model [28,29,30,31,32,33,34,35]. Additionally, in order to compare single molecule calculations with experimental measurements, macroscopic propagation of the emitted radiation field in a gas jet or chamber needs to be carried out, with input from calculations involving hundreds of laser intensities to account for intensity variation near the laser focus.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative rescattering theory for high-order harmonic generation from molecules

et al. 2009

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The Quantitative Rescattering Theory (QRS) for high-order harmonic generation (HHG) by intense laser pulses is presented. According to the QRS, HHG spectra can be expressed as a product of a returning electron wave packet and the photo-recombination differential cross section of the laser-free continuum electron back to the initial bound state. We show that the shape of the returning electron wave packet is determined mostly by the laser only. The returning electron wave packets can be obtained from the strong-field approximation or from the solution of the time-

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Section: A Methods Of Solving the Time-dependent Schrödinger Equationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative rescattering theory for high-order harmonic generation from molecules

et al. 2009

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“…In order to effectively test the various theoretical models of HHG, it is essential to investigate as wide a range of targets as possible . To date the majority of such experiments have been limited to the noble gases, with limited number employing molecular gases such as N 2 , O 2 and CO 2 [19][20][21] in a gas jet geometry. This current work extends upon previous observations to study the harmonic emission in a capillary waveguide from three gases of increasing complexity: atomic Ar and the linear diatomic and triatomic molecules of N 2 and N 2 O respectively.…”

Section: Introductionmentioning

confidence: 99%

Molecular variation of capillary-produced soft x-ray high harmonics

Stebbings¹,

Rogers²,

Paula³

et al. 2008

J. Phys. B: At. Mol. Opt. Phys.

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The production of coherent soft x-rays via high harmonic generation (HHG) from Ar, N 2 and N 2 O in a gas-filled capillary waveguide is reported. Odd harmonics of the driving laser intensity are observed as a function of gas pressure up to energies of 50 eV. By employing a simple phase matching theory that incorporates the spatial and temporal dependences of ionization within the waveguide, good agreement with the HHG spectral envelope has been obtained, indicating phase matching is the dominant factor in shaping the spectral envelope of the harmonics.

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“…This approach will be called either "Lewenstein model" or "SFA" interchangeably in this thesis. SFA has also been applied to study the characteristics of HHG from molecular targets [85][86][87][88][89][90][91][92]. In the following we derive the Lewenstein model for an atomic target in detail, and then it is extended for a molecular target straightforwardly.…”

Section: Strong-field Approximationmentioning

confidence: 99%

Theory of Nonlinear Propagation of High Harmonics Generated in a Gaseous Medium

Jin

2013

Springer Theses

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In this thesis, we establish the theoretical tools to investigate high-order harmonic generation (HHG) by intense infrared lasers in a gaseous medium. The macroscopic propagation of both the fundamental and the harmonic fields is taken into account by solving Maxwell's wave equations, while the single-atom (or single-molecule) response is obtained by quantitative rescattering theory. The initial spatial mode of the fundamental laser is assumed either a Gaussian or a truncated Bessel beam. On the examples of Ar, N 2 and CO 2 , we demonstrate that the available experimental HHG spectra with isotropic and aligned target media can be accurately reproduced theoretically even though the HHG spectra are sensitive to the experimental conditions. We show that the macroscopic HHG can be expressed as a product of a macroscopic wave packet and a photorecombination cross section, where the former depends on laser and experimental conditions while the latter is the property of the target only. The factorization makes it possible to retrieve the single-atom or single-molecule structure information from experimental HHG spectra. As for the multiple molecular orbital contribution in HHG, it causes the disappearance of the minimum in the HHG spectrum of aligned N 2 with the increase of laser intensity, and the position of minimum in HHG spectrum of aligned CO 2 depending on many factors is also attributed to it, which could explain why the minima observed in different laboratories may differ. For an important application of HHG as ultrashort light source, we show that measured continuous harmonic spectrum of Xe due to the reshaping of the fundamental laser field can be used to produce an isolated attosecond pulse by spectral and spatial filtering in the far field. For on-going application of using HHG to ionize aligned molecules, we present the photoelectron angular distribution from aligned N 2 and CO 2 in the laboratory frame, which can be compared directly with future experiments. demonstrate that the available experimental HHG spectra with isotropic and aligned target media can be accurately reproduced theoretically even though the HHG spectra are sensitive to the experimental conditions. We show that the macroscopic HHG can be expressed as a product of a macroscopic wave packet and a photorecombination cross section, where the former depends on laser and experimental conditions while the latter is the property of the target only. The factorization makes it possible to retrieve the single-atom or single-molecule structure information from experimental HHG spectra. As for the multiple molecular orbital contribution in HHG, it causes the disappearance of the minimum in the HHG spectrum of aligned N 2 with the increase of laser intensity, and the position of minimum in HHG spectrum of aligned CO 2 depending on many factors is also attributed to it, which could explain why the minima observed in different laboratories may differ. For an important application of HHG as ultrashort light source, we show that measured continu...

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Molecular orbital dependence of high-order harmonic generation

Cited by 8 publications

References 38 publications

Quantitative rescattering theory for high-order harmonic generation from molecules

Quantitative rescattering theory for high-order harmonic generation from molecules

Molecular variation of capillary-produced soft x-ray high harmonics

Theory of Nonlinear Propagation of High Harmonics Generated in a Gaseous Medium

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