124 research outputs found
Radiation Generated by Charge Migration Following Ionization
Electronic many-body effects alone can be the driving force for an ultrafast
migration of a positive charge created upon ionization of molecular systems.
Here we show that this purely electronic phenomenon generates a characteristic
IR radiation. The situation when the initial ionic wave packet is produced by a
sudden removal of an electron is also studied. It is shown that in this case a
much stronger UV emission is generated. This emission appears as an ultrafast
response of the remaining electrons to the perturbation caused by the sudden
ionization and as such is a universal phenomenon to be expected in every
multielectron system.Comment: 5 pages, 4 figure
Ultrafast interatomic electronic decay in multiply excited clusters
An ultrafast mechanism belonging to the family of interatomic Coulombic decay
(ICD) phenomena is proposed. When two excited species are present, an ultrafast
energy transfer can take place bringing one of them to its ground state and
ionizing the other one. It is shown that if large homoatomic clusters are
exposed to an ultrashort and intense laser pulse whose photon energy is in
resonance with an excitation transition of the cluster constituents, the large
majority of ions will be produced by this ICD mechanism rather than by
two-photon ionization. A related collective-ICD process that is operative in
heteroatomic systems is also discussed.Comment: 4 pages, 3 figure
The role of symmetric vibrational modes in the dehoherence of correlation-driven charge migration
Due to the electron correlation, a fast removal of an electron from a
molecule may create a coherent superposition of cationic states and in this way
initiate pure electronic dynamics in which the hole-charge left by ionization
migrates throughout the system on an ultrashort time scale. The coupling to the
nuclear motion introduces a decoherence that eventually traps the charge and a
crucial question in the field of attochemistry is how long the electronic
coherence lasts and which nuclear degrees of freedom are mostly responsible for
the decoherence. Here, we report full-dimensional quantum calculations of the
concerted electron-nuclear dynamics following outer-valence ionization of
propynamide, which reveal that the pure electronic coherences last only 2-3 fs
before being destroyed by the nuclear motion. Our analysis shows that the
normal modes that are mostly responsible for the fast electronic decoherence
are the symmetric in-plane modes. All other modes have little or no effect on
the charge migration. This information can be useful to guide the development
of reduced dimensionality models for larger systems or the search of molecules
with long coherence times
Quantum Interference Paves the Way for Long-Lived Electronic Coherences
The creation and dynamical fate of a coherent superposition of electronic states generated in a polyatomic molecule by broadband ionization with extreme ultraviolet pulses is studied using the multiconfiguration time-dependent Hartree method together with an ionization continuum model Hamiltonian. The electronic coherence between the hole states usually lasts until the nuclear dynamics leads to decoherence. A key goal of attosecond science is to control the electronic motion and design laser control schemes to retain this coherence for longer timescales. Here, we investigate this possibility using time-delayed pulses and show how this opens up the prospect of coherent control of charge migration phenomenon
Attosecond spectroscopy reveals alignment dependent core-hole dynamics in the ICl molecule.
The removal of electrons located in the core shells of molecules creates transient states that live between a few femtoseconds to attoseconds. Owing to these short lifetimes, time-resolved studies of these states are challenging and complex molecular dynamics driven solely by electronic correlation are difficult to observe. Here, we obtain few-femtosecond core-excited state lifetimes of iodine monochloride by using attosecond transient absorption on iodine 4d-16p transitions around 55 eV. Core-level ligand field splitting allows direct access of excited states aligned along and perpendicular to the ICl molecular axis. Lifetimes of 3.5 ± 0.4 fs and 4.3 ± 0.4 fs are obtained for core-hole states parallel to the bond and 6.5 ± 0.6 fs and 6.9 ± 0.6 fs for perpendicular states, while nuclear motion is essentially frozen on this timescale. Theory shows that the dramatic decrease of lifetime for core-vacancies parallel to the covalent bond is a manifestation of non-local interactions with the neighboring Cl atom of ICl
- …