Molecular Recollision Interferometry in High Harmonic Generation

Abstract

We use extreme-ultraviolet interferometry to measure the phase of high-order harmonic generation from transiently aligned CO(2) molecules. We unambiguously observe a reversal in phase of the high-order harmonic emission for higher harmonic orders with a sufficient degree of alignment. This results from molecular-scale quantum interferences between the molecular electronic wave function and the recolliding electron as it recombines with the molecule, and is consistent with a two-center model. Furthermore, using the combined harmonic intensity and phase information, we extract accurate information on the dispersion relation of the returning electron wave packet as a function of harmonic order. This analysis shows evidence of the effect of the molecular potential on the recolliding electron wave.

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

“…x cos( 1 2 kR cos θ ) [22,25]. Then the variation φ of the polarization direction on varying θ in the vicinity of θ p is proportional to (kR cos θ ) (π/ cos θ p ) (cos θ ).…”

High-order-harmonic generation from field-distorted orbitals

“…Apart from being a source of coherent XUV radiation [1,2], and ultrafast pulses [3][4][5], the process of HHG has also been used to extract internuclear separations [6][7][8][9] and electronic orbitals [10][11][12][13][14]. The intrinsic timing in the HHG process associated with the time from ionization to recombination can, e.g., be used to resolve nuclear dynamics on an ultrafast timescale [6][7][8].…”

Linked attosecond phase interferometry for molecular frame measurements

“…(1) A two-source interferometer measures the phase versus molecular angle, Φ M ol (θ; q), and (2) aligned target molecule mixed with a reference atom is recorded. Each of these steps has been previously demonstrated [8,[17][18][19]. The difficulty until now was the lack of coupling between the two coordinates q and θ of the two-dimensional phase Φ M ol (q, θ).…”

“…As illustrated in Fig. 2(a), we obtain two identical XUV sources by spatially splitting the incoming laser beam using refractive elements placed between the focusing mirror and the gas jet [17] (refer to the Supplementary Information (SI) section I for experimental details). Using a thin gas jet allows us to minimize propagation effects and, therefore, to measure the single-molecule response at the XUV detector [4].…”