Analysis of recombination in high-order harmonic generation in molecules

Abstract

We show that the dependence of high-order harmonic generation (HHG) on the molecular orientation can be understood within a theoretical treatment that does not involve the strong field of the laser. The results for H2 show excellent agreement with time-dependent strong field calculations for model molecules, and this motivates a prediction for the orientation dependence of HHG from the N2 3σg valence orbital. For both molecules, we find that the polarization of recombination photons is influenced by the molecular orientation. The variations are particularly pronounced for the N2 valence orbital, which can be explained by the presence of atomic p-orbitals.

Quantitative rescattering theory for high-order harmonic generation from molecules

“…However, N 2 minima do not follow any simple pattern. This fact has been noticed earlier by Zimmermann et al [97]. This clearly indicates that the two-center interference model is not guarantied to work a priori.…”

High-order-harmonic generation from field-distorted orbitals

“…Yet the two-center interference minimum, though theoretically predicted [28,29], has never been observed experimentally [10,23,30]. We explain the lack of a two-center interference minimum in terms of laser-induced orbital distortion.…”

Role of resonance-enhanced multiphoton excitation in high-harmonic generation of N2: A time-dependent density-functional-theory study

“…Two-center interference [13] has also been discussed by Zimmermann et al [28] and Gühr et al [29]. Zimmermann et al observed that the 3σ g orbital of N 2 is a linear combination of p and s orbitals at the two atomic centers.…”

“…With the REME and Rydberg orbital considered, we propose a model that has two major differences compared to earlier work by Lein et al [13] and by Zimmermann et al [28]. (i) Since we identify the Rydberg orbital (2pσ u ) rather than the HOMO (2pσ g ) as the MO for recombination, the destructive interference requires the free-electron plane wave to have a π phase difference between the atomic centers, rather than a difference of 2π , i.e.,…”