Electron-nuclear correlation in above-threshold double ionization of molecules

Abstract

We report on the experimental observation of photon energy sharing among two electrons and two ions ejected from a doubly ionized molecule exposed to an intense ultraviolet femtosecond laser pulse. Although two electrons are successively released one after the other, bridged by the nuclear motion via their interactions, photon energy sharing among four particles is observed as multiple energy conservation lines in their joint energy spectrum. For sequential double ionization of H 2 , the electron-nuclear joint energy spectrum allows us to identify three pathways towards the charge-resonance enhanced ionization of the stretching H 2 + in strong laser fields. By counting the photon number absorbed by the molecule, we trace the accessibility, enhancement, and suppression of various pathways. The correlated electron-nuclear motion provides profound insights of the complicated strong-field dynamics of molecules.

Electron-nuclear correlated multiphoton-route to Rydberg fragments of molecules

“…2b, the tilted strips in the JES can be distinguished into three distinct regions with E N in the ranges of 2.0–3.0, 3.0–5.0, and 5.0–7.0 eV (marked by the white arrows), indicating three distinct pathways in producing the (H + , H + ) channel. The generation of (H + , H + ) channel can be described by a three-step process 45–47 . As sketched in Fig.…”

Clocking Enhanced Ionization of Hydrogen Molecules with Rotational Wave Packets

“…Intense light can couple nuclear and electron dynamics leading to hallmark phenomena of molecular strong-field physics such as correlated electron-nuclear energy sharing [1][2][3], bond softening [4], bond hardening [5], abovethreshold dissociation [2,6,7], light-induced conical and nonconical intersections [8,9], and enhanced ionization [10,11], all of which have been extensively studied in the hydrogen molecule H 2 (see, e.g., Refs. [12][13][14][15], and references therein).…”

Photon-number-resolved asymmetric dissociative single ionization of H2

“…To unambiguously count the total number of photons absorbed by the molecule in the ionization and dissociation steps, the electron-nuclear JES is employed. As compared to atoms, the multiphoton above threshold ionization (ATI) of the molecules may produce discrete diagonal lines in the JES as a consequence of the correlated sharing of the absorbed photon energy above the ionization threshold among the outgoing electron and nuclear fragments [36][37][38][39][40][41][42][43][44][45]. Each diagonal line indicates that the molecule as a whole absorbs a constant number of photons, i.e., the sum energy of the ejected electron and nuclear fragments E sum = E N + E e = mhω − (I p0 + U p ).…”

“…When exposed to a strong laser field, the electrons and nuclei of a molecule as a whole absorb multiple photons in the ionization and dissociation steps. As compared to the atoms, the electrons and nuclei of a molecule share the absorbed photon energy [36][37][38][39][40][41][42][43][44][45], i.e., the photon energy is correlatively partitioned between electrons and nuclei. Until now, the role of the photon energy sharing between the electron and nuclei on directional breaking of molecules has not been explicitly explored, in particular, the dependence on the total number of the photons absorbed by the molecule in the ionization and dissociation processes.…”