Fully Differential Single-Photon Double Ionization of Neon and Argon

Abstract

Triply differential cross sections are calculated for one-photon double ionization of neon and argon at various photon energies and electron energy sharings by using a frozen-core treatment to represent the remaining electrons of the residual ion. Angular distributions agree well with all existing experimental data, showing that in spite of its simplicity the method can treat the double ionization of complex targets reliably. A comparison of the cross sections for helium, neon, and argon into the same final state symmetry at the same relative excess energies reveals a distinctive signature of the role of electron correlation in each target. DOI: 10.1103/PhysRevLett.110.173001 PACS numbers: 32.80.Fb, 34.10.+x One-photon double photoionization (DPI) of atomic targets is a fundamental problem that has been the subject of significant investigation because of the explicitly correlated nature of the process. The simplest target where DPI can occur is helium, for which experiments using coincidence measurements of the resulting Coulomb fragments allow description of the fully differential electron dynamics. In parallel, ab initio theoretical treatments of helium DPI have produced results in excellent agreement with experiment: Double ionization of helium can be considered a solved problem (see, e.g., Refs. [1][2][3][4][5], and references therein). In contrast, for heavier rare-gas atoms, the volume of experimental measurements of one-photon DPI greatly outweighs the theoretical data, which have been confined to model treatments [6] and parameterization of the process [7,8]. At the same time, significant interest in studying rare-gas targets in laser-atom interactions has evolved beyond the single-photon perturbative limit of DPI. Processes such as high-harmonic generation [9], attosecond streaking [10], and multiphoton ionization [11] with coherent light sources represent some of the most recent examples of the evolving scope for investigating multielectron dynamics in rare gases. Application of precise and kinematically complete experimental techniques has outpaced the capacity for absolute theoretical treatments to fully represent the total correlated dynamics in rare-gas targets beyond helium. For single-photon DPI of neon or argon, no accurate fully ab initio description of this process has been achieved.Here we report the results of a method that makes use of a fully correlated grid-based expansion to describe the electrons ejected into the double continuum in the presence of the remaining bound electrons that advances our theoretical capacity to describe DPI in many-electron atomic targets. The key to this framework is the construction of an atomic orbital basis that represents the bound N À 2 electrons, which will remain frozen throughout the double ionization process [12]. Thus the final state represents two indistinguishable continuum electrons that will share the excess photon energy in the presence of those electrons remaining bound to the parent ion. The proper description of the angular distributions a...

Time-dependentR-matrix theory applied to two-photon double ionization of He

“…More recently, it has been concluded, however, that accurate cross sections can be obtained using either exterior complex scaling (ECS) or through projection onto Coulomb functions, if the wavefunction is propagated for sufficiently long times and sufficiently long distances [13]. Although significant effort has been devoted to describe multiphoton double ionization processes in helium, the accurate description of double photoionization processes for general multi-electron atoms from first principles is still in its infancy, even after absorption of only a single photon [14].…”

Dissociation dynamics of the water dication following one-photon double ionization. I. Theory

“…The current state of the art for ab initio calculation of double photoionization amplitudes is to treat the dynamics of two active electrons completely while freezing the others in target atomic or molecular orbitals. Such calculations have only been carried out on atoms [38][39][40][41][70][71][72][73] to our knowledge, but in those cases surprisingly good agreement with experimental angular distributions of the ejected electrons was obtained. To calculate the TDCS for onephoton double ionization of water, we can make the same two-active-electron approximation, and use the computational methods involving a single center expansion and numerical grids that we have used previously in double photoionization calculations on H 2 [47][48][49][50].…”

Hybrid Gaussian–discrete-variable representation for one- and two-active-electron continuum calculations in molecules

“…This has been demonstrated both where the nonionized electrons form a spherically symmetric singlet closed shell [16][17][18] and for atoms whose residual dication is left behind in open-shell configurations of various spin multiplicities [19,20]. The results are remarkably accurate compared with experimental measurements, thus indicating that a first step to being able to treat double ionization in targets with more than only two electrons can proceed as long as: (1) electron correlation of those electrons to be moved into the continuum by the photoabsorption are treated precisely, and (2) the interaction of these outgoing electrons with those of the residual target be accounted for, at least, in an average way.…”