High Harmonic Generation and the Role of Atomic Orbital Wave Functions

Lévesque, Julie; Zeidler, D.; Marangos, J. P.; Corkum, P. B.; Villeneuve, D. M.

doi:10.1103/physrevlett.98.183903

Cited by 104 publications

(96 citation statements)

References 31 publications

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“…This model has been assumed in Itatani et al [66] and in Levesque et al [132]. Our results confirm the validity of their assumptions.…”

Section: Independence Of Wave Packet On Targetssupporting

confidence: 81%

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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“…This model has been assumed in Itatani et al [66] and in Levesque et al [132]. Our results confirm the validity of their assumptions.…”

Section: Independence Of Wave Packet On Targetssupporting

confidence: 81%

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

Jin

2013

Springer Theses

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“…Even for the 15-cycle pulse the depletion of the ground state remains below 6%. The results suggest that when using the planewave approximation for the returning electron in molecular imaging applications, a dispersion relationship in between the Lewenstein and I p -corrected relationships should be used [18,19].…”

Section: Harmonic Intensitymentioning

confidence: 99%

Two-center interference and ellipticity in high-order harmonic generation fromH2+

Zwan

Lein

2010

Phys. Rev. A

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We present a theoretical investigation into the two-center interference in aligned H + 2 . The influence of the laser field on the recombination step is investigated by comparing laser-induced harmonic generation with harmonic generation from field-free collisions of Gaussian wave packets with the core. We find that for different Gaussian wave packets colliding with the molecule, the interference minimum occurs at the same alignment angle. The same result is obtained for the laser-induced spectrum when only a single electronic trajectory per harmonic contributes. When multiple electronic trajectories contribute, we find an effect on the minimum position because the interference between short and long trajectories is alignment dependent. The two-center interference and the influence of the Coulombic potential are clearly seen not only in the harmonic intensity and phase but also in the polarization direction and ellipticity. We observe significant ellipticity of the emitted radiation around the two-center interference minimum.

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“…We Fourier transform the superimposed dipole matrix elements and multiply the absolute value by ω 4 to find the HHG spectral intensity [49]. We observe a minimum and an associated phase jump in the N 2 HHG spectrum.…”

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confidence: 99%

High-order harmonic phase in molecular nitrogen

et al. 2009

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Electronic structure in atoms and molecules modulates the amplitude and phase of high harmonic generation (HHG). We report measurements of the high harmonic spectral amplitude and phase in N 2 . The phase is measured interferometrically by beating the N 2 harmonics with those of an Ar reference oscillator in a gas mixture. A rapid phase shift of 0.2π is observed in the vicinity of the HHG spectral minimum, where a shift of π had been presumed [J. Itatani et al., Nature 432, 867 (2004)]. We compare the phase measurements to a simulation of the HHG recombination step in N 2 that is based on a simple interference model. The results of the simulation suggest that modifications beyond the simple interference model are needed to explain HHG spectra in molecules.

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High Harmonic Generation and the Role of Atomic Orbital Wave Functions

Cited by 104 publications

References 31 publications

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

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

Two-center interference and ellipticity in high-order harmonic generation fromH2+

High-order harmonic phase in molecular nitrogen

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