Probing Electron Correlation via Attosecond xuv Pulses in the Two-Photon Double Ionization of Helium

Feist, Johannes; Nagele, Stefan; Pazourek, Renate; Persson, Emil; Schneider, Barry I.; Collins, L. A.; Burgdörfer, Joachim

doi:10.1103/physrevlett.103.063002

Cited by 108 publications

(103 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[5,[34][35][36]. For systems with interacting electrons, only very few cases are manageable without approximations, such as helium and H 2 [37][38][39][40][41][42][43][44][45], and even in these cases the whole range of laser frequencies and intensities can not be accessed.…”

Section: Theorymentioning

confidence: 99%

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

2014

View full text Add to dashboard Cite

We present a wave-function based method to solve the time-dependent many-electron Schrödinger equation (TDSE) with special emphasis on strong-field ionization phenomena. The theory builds on the configuration-interaction (CI) approach supplemented by the generalized-active-space (GAS) concept from quantum chemistry. The latter allows for a controllable reduction in the number of configurations in the CI expansion by imposing restrictions on the active orbital space. The method is similar to the recently formulated time-dependent restricted-active-space (TD-RAS) CI method [D. Hochstuhl, and M. Bonitz, Phys. Rev. A 86, 053424 (2012)]. We present details of our implementation and address convergence properties with respect to the active spaces and the associated account of electron correlation in both ground state and excitation scenarios. We apply the TD-GASCI theory to strong-field ionization of polar diatomic molecules and illustrate how the method allows us to uncover a strong correlation-induced shift of the preferred direction of emission of photoelectrons.

show abstract

Section: Theorymentioning

confidence: 99%

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

2014

View full text Add to dashboard Cite

show abstract

“…The rapid oscillations of continuum orbitals are better described by dedicated radial sets like, e.g., finite-element discrete-variable representations [38][39][40][41][42][43] and B splines [44][45][46][47]. The use of this latter type of function, however, leads to costly polycentric bielectronic integrals or, alternatively, to monocentric expansions which converge too slowly except for the simplest cases (e.g., H 2 [48] and hydrides of light elements [49,50]).…”

Section: Introductionmentioning

confidence: 99%

Hybrid Gaussian–B-spline basis for the electronic continuum: Photoionization of atomic hydrogen

2014

View full text Add to dashboard Cite

As a first step towards meeting the recent demand for new computational tools capable of reproducing molecular-ionization continua in a wide energy range, we introduce a hybrid Gaussian-B-spline basis (GABS) that combines short-range Gaussian functions, compatible with standard quantum-chemistry computational codes, with B splines, a basis appropriate to represent electronic continua. We illustrate the performance of the GABS hybrid basis for the hydrogen atom by solving both the time-independent and the time-dependent Schrödinger equation for a few representative cases. The results are in excellent agreement with those obtained with a purely B-spline basis, with analytical results, when available, and with recent above-threshold ionization spectra from the literature. In the latter case, we report fully differential photoelectron distributions which offer further insight into the process of above-threshold ionization at different wavelengths.

show abstract

“…Two-photon double ionization is much more difficult to detect than singlephoton double ionization due to its extremely small total cross section (≈10 −52 cm 4 s) [17][18][19]. It was first measured in 2005 [18], followed by many theoretical studies [16,17,[19][20][21][22][23][24][25].…”

mentioning

confidence: 99%

Criterion for Distinguishing Sequential from Nonsequential Contributions to the Double Ionization of Helium in Ultrashort Extreme-Ultraviolet Pulses

Liu

Thumm

2015

Phys. Rev. Lett.

View full text Add to dashboard Cite

We quantify sequential and nonsequential contributions in two-photon double ionization of helium atoms by intense ultrashort extreme-ultraviolet pulses with central photon energies ℏω ctr near the sequential double-ionization threshold. If the spectrum of such pulses overlaps both the sequential (ℏω > 54.4 eV) and nonsequential (ℏω < 54.4 eV) double-ionization regimes, the sequential and nonsequential doubleionization mechanisms are difficult to distinguish. By tracking the double-ionization asymmetry in joint photoelectron angular distributions, we introduce the two-electron forward-backward-emission asymmetry as a measure that allows the distinction of sequential and nonsequential contributions. Specifically, for ℏω ctr ¼ 50 eV pulses with a sine-squared temporal profile, we find that the sequential double-ionization contribution is the largest at a pulse length of 650 as, due to competing temporal and spectral constraints. In addition, we validate a simple heuristic expression for the sequential double-ionization contribution in comparison with ab initio calculations. DOI: 10.1103/PhysRevLett.115.183002 PACS numbers: 32.80.Rm, 33.80.Rv, 42.50.Hz In 1975, the mechanism of nonsequential double ionization was revealed in the photoionization of alkaline earth atoms [1]. It is enabled by strong electronic correlation and thus clearly distinct from the sequential double-ionization mechanism. Nonsequential double ionization was observed for noble gas atoms in 1982 [2] and received rapidly increasing attention from both experimentalists [3-9] and theorists [10][11][12][13].Photoelectron angular distributions of single-photon double ionization were found to owe their structure partly to (dipole) selection rules [11,14,15] and to consist of symmetrical and antisymmetrical contributions (with regard to electron exchange), that each can be written as the product of an angular and a correlation factor [11]. For coplanar emission geometry, where the emitted-electron momenta and polarization axis of the linearly polarized extremeultraviolet (XUV) pulse lie in a plane, and for equal energy sharing (equal asymptotic kinetic energies E 1 and E 2 of the photoelectrons), the angular factor becomes j cos θ 1 þ cos θ 2 j 2 , where θ 1 and θ 2 are photoelectron emission angles relative to the polarization direction of the ionizing light, while the electron correlation factor follows as expf−4 ln 2½ðθ 12 − πÞ=θ 1=2 2 g, with the mutual emission angle θ 12 ¼ jθ 1 − θ 2 j. The adjustable parameter, θ 1=2 , is related to the significance of correlation in the double-ionization process [11]. The antisymmetrical contribution and back-to-back electron emission vanish at equal energy sharing but become progressively more prominent for increasingly nonequal energy sharing, as the antisymmetrical contribution j cos θ 1 − cos θ 2 j 2 gradually appears in joint photoelectron angular distributions [10,11,16].

show abstract

Probing Electron Correlation via Attosecond xuv Pulses in the Two-Photon Double Ionization of Helium

Cited by 108 publications

References 33 publications

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

Hybrid Gaussian–B-spline basis for the electronic continuum: Photoionization of atomic hydrogen

Criterion for Distinguishing Sequential from Nonsequential Contributions to the Double Ionization of Helium in Ultrashort Extreme-Ultraviolet Pulses

Contact Info

Product

Resources

About