arXiv subjects

Matthew Benjamin Peters

Publications and source records attributed to Matthew Benjamin Peters.

4 recordsLinked to original sources

arXiv2023

A general model and toolkit for the ionization of three or more electrons in strongly driven molecules using an effective Coulomb potential for the interaction between bound electrons

We formulate a general three-dimensional semiclassical model for the study of correlated multielectron escape during fragmentation of molecules driven by intense infrared laser pulses, while fully accounting for the magnetic field of the laser pulse. We do so in the context of triple ionization of strongly driven HeH$_{2}^{+}$. Our model fully accounts for the singularity in the Coulomb potentials of a recolliding electron with the core and a bound electron with the core as well as for the interaction of a recolliding with a bound electron. To avoid artificial autoionization, our model employs effective potentials to treat the interaction between bound electrons. We focus on triple and double ionization as well as frustrated triple and frustrated double ionization. In these processes, we identify and explain the main features of the sum of the kinetic energies of the final ion fragments. We find that frustrated double ionization is a major ionization process, and we identify the different channels and hence different final fragments that are obtained through frustrated double ionization. Also, we discuss the differences between frustrated double and triple ionization.

physics.atom-ph↗

arXiv2023

Nondipole electron momentum offset as a probe of correlated three electron ionization in strongly driven atoms

We employ a recently developed three-dimensional semiclassical model to identify nondipole effects in triple ionization of Ne driven by infrared laser pulses at intensities where electron-electron correlation prevails. This model fully accounts for the Coulomb interaction of each electron with the core and avoids artificial autoionization by employing effective Coulomb potentials to describe the interaction between bound electrons (ECBB). Using the ECBB model, we identify a prominent signature of nondipole effects. Namely, the component along the direction of light propagation of the average sum of the final electron momenta is large and positive. That is, we identify a positive momentum offset, absent in the dipole approximation. We find that this positive momentum offset stems mostly from the momentum change due to the magnetic field. To further understand this momentum change, we also develop a simple model for the motion of an electron inside an electromagnetic field. This simple model accounts for the effect of the Coulomb forces only as a sharp change in the momentum of the electron during recollision. We show that the momentum change due to the magnetic field is related with the sharp change in momentum during recollision for the recolliding electron as well as with the time of recollision for both the recolliding and bound electrons. Hence, we demonstrate that the final electron momentum offset probes the strength of a recollision and hence the degree of correlation in multielectron ionization.

physics.atom-ph↗

arXiv2023

Singularity in electron-core potential as a gateway to accurate multi-electron ionization spectra in strongly driven atoms

We demonstrate a general three-dimensional semiclassical model as a powerful technique for the study of correlated multi-electron escape in atoms driven by infrared laser pulses at intensities where electron-electron correlation prevails. We do so in the context of triple ionization of strongly driven Ne. We show that a drawback of other current quantum mechanical and classical models of triple ionization is that they soften the Coulomb potential of each electron with the core. The model we employ fully accounts for the singularity in the Coulomb potentials of a recolliding electron with the core and a bound electron with the core as well as for the interaction of a recolliding with a bound electron. Our model treats approximately only the interaction between bound electrons through the use of effective potentials. These effective potentials ensure that no artificial autoionization takes place as a result of the full treatment of the electron-core potential. We demonstrate the accuracy of our model by obtaining triple ionization distributions of the sum of the final electron momenta which we find to be in very good agreement with experiments. Also, we explain the main features of these momenta distributions in terms of the prevalent pathways of correlated three-electron escape in Ne. We also show that the different ionization pathways prevailing in three-electron escape in strongly driven Ne versus Ar give rise to different momenta distributions in these two atoms.

physics.atom-ph↗

arXiv2020

Signatures of magnetic field effects in non-sequential double ionization manifesting as back-scattering for molecules versus forward-scattering for atoms

For two-electron diatomic molecules, we investigate magnetic field effects in non-sequential double ionization where recollisions prevail. We do so by formulating a three-dimensional semi-classical model that fully accounts for the Coulomb singularities and for magnetic field effects during time propagation. Using this model, we identify a prominent signature of non-dipole effects. Namely, we demonstrate that the recolliding electron back-scatters along the direction of light propagation. Hence, this electron escapes opposite to the direction of change in momentum due to the magnetic field. This is in striking contrast to strongly-driven atoms where the recolliding electron forward-scatters along the direction of light propagation. We attribute these distinct signatures to the different gate that the magnetic field creates jointly with a soft recollision in molecules compared to a hard recollision in atoms. These two different gates give rise, shortly before recollision, to different momenta and positions of the recolliding electron along the direction of light propagation. As a result, we show that the Coulomb forces from the nuclei act to back-scatter the recolliding electron in molecules and forward-scatter it in atoms along the direction of light propagation.

physics.atom-ph↗