Semiclassical-wave-function perspective on high-harmonic generation

Abstract

We introduce a semi-classical wavefunction (SCWF) model for strong-field physics and attosecond science. When applied to high harmonic generation (HHG), this formalism allows one to show that the natural time-domain separation of the contribution of ionization, propagation and recollisions to the HHG process leads to a frequency-domain factorization of the harmonic yield into these same contributions, for any choice of atomic or molecular potential. We first derive the factorization from the natural expression of the dipole signal in the temporal domain by using a reference system, as in the quantitative rescattering (QRS) formalism [J. Phys. B. 43, 122001 (2010)]. Alternatively, we show how the trajectory component of the SCWF can be used to express the factorization, which also allows one to attribute individual contributions to the spectrum to the underlying trajectories.

High-harmonic spectroscopy of transient two-center interference calculated with time-dependent density-functional theory

“…The scattering term in Eq. (2) is often described as the field-free cross-section 52 true⟨ψb|d^|ψctrue(ν;θtrue)true⟩,where ψ b is the bound-component part of the wave function—or an orbital representation in DFT frameworks—and d^ is the dipole/velocity/acceleration operator. ψ c represents a normalized continuum state with the momentum mapped to the HHG emission energy ν and the rescattering angle θ .…”

Orbital-resolved calculations of two-center interferences in linear triatomic molecules

“…This trend is expected as the carbon-chalcogen bond length increases with heavier elements, and the energy of the TCI feature is expected to qualitatively scale as the inverse of the charge-separation distance squared [53,54]. Quantitative deviations from the plane-wave scattering prediction for the TCI are attributed to the Coulomb tail and target-specific potentials for each compound [16,48,51].…”

“…TDDFT HHG spectra contain the target-specific features associated with the carbon dichalcogen TCI, alongside generic contributions that we would like to get rid of. In the quantitative rescattering (QRS) formalism, the complex HHG spectrum is factorized as [48][49][50][51] HHG k (θ, ν) = I(θ)…”

Signature of charge migration in modulations of double ionization

“…On the other hand, the ionized electron component is described with a oneelectron continuum, which we generically label with |v . Depending on the degree of precision required, one can use, e.g., plane waves/Volkov states, Coulomb waves [56], exact one-electron continuum states [57].…”

“…Assuming one can generalize the notion of such dressed states to oscillating fields (see section VI), it opens a clear perspective for extending quantitative rescattering (QRS) results [65] and similar HHG spectrum factorization [66] to multichannel processes. This would be done by performing the temporal to frequency factorization [57] for each dressed channel independently, and coherently summing all contributions. We stress that this is possible only because the dressed channels are virtually independent systems.…”