Dissociative ionization ofH2+: Few-cycle effect in the joint electron-ion energy spectrum

Abstract

Joint electron-ion energy spectra for the dissociative ionization of a model H + 2 in few-cycle, infrared laser pulses are calculated via the numerical ab initio solution of the time-dependent Schrödinger equation. A strong, pulse-dependent modulation of the ionization probability for certain values of the protons' kinetic energy (but almost independent of the electron's energy) is observed. With the help of models with frozen ions, this featurewhich mistakenly might be attributed to vibrational excitations-is traced back to the transient population of electronically excited states, followed by ionization. This assertion is further corroborated employing a twolevel model incorporating strong-field ionization from the excited state.

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.…”

Photon Energy Deposition in Strong-Field Single Ionization of Multielectron Molecules

“…The excess photon energy over the ionization threshold is not only deposited to the outgoing electron, but also transferred to the heavy nuclei via their correlated interactions. As compared to the H 2 þ [20][21][22][23][24][25][26][27] or H 2 [28], the light may directly interact with the nuclei for the heteronuclear diatomic molecule having a permanent dipole. However, for CO the dipole moments of the nuclei and the three highest occupied molecular orbitals (HOMOs) are estimated to be 0.0028 (nuclei), 0.4486 (HOMO), 0.2909 (HOMO-1), and 0.3232 Debye (HOMO-2), respectively.…”

“…Until recently, the electron-nuclear sharing of the absorbed photon energy in strong-field multiphoton single ionization of molecules was revealed for the simplest one-or twoelectron systems of H 2 þ [20][21][22][23][24][25][26][27] and H 2 [28]. On the other hand, the recent experiments showed negligible photon energy sharing between the emitted electrons and ions in double ionization of a polyatomic hydrocarbon molecule [29].…”

Time-dependent renormalized-natural-orbital theory applied to laser-drivenH2+

“…In this paper, we extend the recently introduced time-dependent renormalized-natural-orbital theory (TDRNOT) [27][28][29][30] towards the simplest molecular system, H + 2 , taking both the electronic and nuclear degrees of freedom fully quantum mechanically into account. We restrict ourselves to a low-dimensional H + 2 model system [20,23,26,[31][32][33][34] in order to have the TDSE benchmark results readily available. However, the TDRNOT equations derived in this work are easily generalized to the "real," three-dimensional (3D) H + 2 .…”