José Luis Sanz-Vicario

University of Antioquia, Medellín, Antioquia, Colombia

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Publications (50)111.35 Total impact

  • Alicia Palacios · José Luis Sanz-Vicario · Fernando Martín
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    ABSTRACT: Attosecond science, born at the beginning of this century with the generation of the first bursts of light with durations shorter than a femtosecond, has opened the way to look at electron dynamics in atoms and molecules at its natural timescale. Thus controlling chemical reactions at the electronic level or obtaining time-resolved images of the electronic motion has become a goal for many physics and chemistry laboratories all over the world. The new experimental capabilities have spurred the development of sophisticated theoretical methods that can accurately predict phenomena occurring in the sub-fs timescale. This review provides an overview of the capabilities of existing theoretical tools to describe electron and nuclear dynamics resulting from the interaction of femto- and attosecond UV/XUV radiation with simple molecular targets. We describe one of these methods in more detail, the time-dependent Feshbach close-coupling (TDFCC) formalism, which has been used successfully over the years to investigate various attosecond phenomena in the hydrogen molecule and can easily be extended to other diatomics. In addition to describing the details of the method and discussing its advantages and limitations, we also provide examples of the new physics that one can learn by applying it to different problems: from the study of the autoionization decay that follows attosecond UV excitation to the imaging of the coupled electron and nuclear dynamics in H2 using different UV-pump/IR-probe and UV-pump/UV-probe schemes.
    No preview · Article · Dec 2015 · Journal of Physics B Atomic Molecular and Optical Physics
  • Andrés F Ordóñez-Lasso · José L Sanz-Vicario · Fernando Martín

    No preview · Article · Sep 2015 · Journal of Physics Conference Series
  • Andrés F Ordóñez-Lasso · José L Sanz-Vicario · Fernando Martín
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    ABSTRACT: We perform a systematic study on the behaviour of energy positions and autoionization widths of metastable resonance states in the Hydrogen molecule subject to screened Coulomb interactions among all particles using an ab initio Feshbach configuration interaction method. We only focus on the Q1 series of doubly excited states lying between the first H2+(1sσg) and the second H2+(2pσu) ionization thresholds, for several spectroscopic molecular symmetries 1,3Σg u, 1,3Πg, u and 1,3Δg, u. Special attention is given to the efficient and accurate method for the evaluation of screened Coulomb two-electron integrals in molecules when using configurations in terms of molecular orbitals described using a B-spline basis.
    No preview · Article · Sep 2015 · Journal of Physics Conference Series
  • J. P. Restrepo Cuartas · J. L. Sanz-Vicario
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    ABSTRACT: Shannon entropy and Fisher information calculated from one-particle density distributions and von Neumann and linear entropies (the latter two as measures of entanglement) computed from the reduced one-particle density matrix are analyzed for the Se1,3,Po1,3, and De1,3 Rydberg series of He doubly excited states below the second ionization threshold. In contrast with the Shannon entropy, we find that both the Fisher information and entanglement measures are able to discriminate low-energy resonances pertaining to different (K,T)n2A2 series according to the Herrick-Sinanoğlu-Lin classification. Contrary to bound states, which show a clear and unique asymptotic value for both Fisher information and entanglement measures in their Rydberg series 1snℓ for n→∞ (which implies a loss of spatial entanglement), the variety of behaviors and asymptotic values of entanglement above the noninteracting limit value in the Rydberg series of doubly excited states (K,T)n2A2 indicates a signature of the intrinsic complexity and remnant entanglement in these high-lying resonances even with infinite excitation n2→∞, for which all known attempts of resonance classifications fail in helium.
    No preview · Article · May 2015 · Physical Review A
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    ABSTRACT: The presence of net circular dichroism in the photoionization of nonchiral homonuclear molecules has been put in evidence recently through the measurement of molecular-frame photoelectron angular distributions in dissociative photoionization of ${\text{H}}_{2}$ [Dowek et al., Phys. Rev. Lett. 104, 233003 (2010)]. In this work we present a detailed study of circular dichroism in the photoelectron angular distributions of ${\text{H}}_{2}$ and ${\text{D}}_{2}$ molecules, oriented perpendicularly to the propagation vector of the circularly polarized light, at different photon energies (20, 27, and 32.5 eV). Circular dichroism in the angular distributions at 20 and to a large extent 27 eV exhibits the usual pattern in which inversion symmetry is preserved. In contrast, at 32.5 eV, the inversion symmetry breaks down, which eventually leads to total circular dichroism after integration over the polar emission angle. Time-dependent ab initio calculations support and explain the observed results for ${\text{H}}_{2}$ in terms of quantum interferences between direct photoionization and delayed autoionization from the ${\mathcal{Q}}_{1}$ and ${\mathcal{Q}}_{2}$ doubly excited states into ionic states $(1s{$\sigma${}}_{g}$ and $2p{$\sigma${}}_{u})$ of different inversion symmetry. Nevertheless, for ${\text{D}}_{2}$ at 32.5 eV, there is a particular case where theory and experiment disagree in the magnitude of the symmetry breaking: when ${\text{D}}^{+}$ ions are produced with an energy of around 5 eV. This reflects the subleties associated to such simple molecules when exposed to this fine scrutiny.
    Full-text · Article · Oct 2014 · Physical Review A
  • J P Restrepo · J L Sanz-Vicario
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    ABSTRACT: Shannon entropies and Fisher information calculated from one-particle density distributions and von Neumann and linear entropies (the latter two as a measure of entanglement) computed from the reduced oneparticle density matrix are analyzed for the S-1,3(e),P-1,3(o) and D-1,3(e) Rydberg series of He doubly excited states below the second ionization threshold. We find that both Fisher information and entanglement measures are able to discriminate resonances pertaining to different (K, T)(A) series.
    No preview · Article · Apr 2014 · Journal of Physics Conference Series
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    José Luis Sanz-Vicario · Carlos Mario Granados-Castro
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    ABSTRACT: A time-dependent Feshbach formalism is proposed to study the resonant photoionization of the helium atom using ultrashort laser pulses. This spectral method consist in solving the time-dependent Schrodinger equation by expanding the time-dependent wavepacket in terms of eigenfunctions defined in two orthogonal halfspaces: a bound-like resonant and a non-resonant scattering-like . The latter eigenfunctions for the projected Hamiltonians H and H are not indeed eigenfunctions of the total Hamiltonian, so that the electrostatic coupling H acts as a leaking operator → responsible for the temporal decay of resonances into the underlying continuum, keeping the physical insight of the Fano-Feshbach time independent formalisms. This method allows not only for accurate descriptions of the resonance parameters (energies, widths and Fano shape parameters) but also for the temporal evolution of the photodynamics involved in the resonant photoionization when using short laser pulses. We illustrate the performance of the method by analyzing the temporal formation of i) the one-photon ionization cross section below the second ionization threshold and the buildup of Fano profiles and ii) the up-down asymmetry of photoelectron angular distributions resulting from interferences of S-, P- and D-waves after simultaneous photoexcitation and decay of the lowest 1Se, 1P° and 1De resonant states, by using two sequential laser pulses with XUV harmonic frequencies separated by a time delay.
    Full-text · Article · Apr 2014 · Journal of Physics Conference Series
  • A F Ordóñez · J C Cardona · J L Sanz-Vicario
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    ABSTRACT: The stability of resonant states in Helium-like atoms while under the influence of a plasma environment is studied. We analyze the variation of resonance parameters (energies and lifetimes) against the strength of the screening parameter within the Debye-Hückel model. We use a Feshbach-like projection formalism with explicitly correlated CI-wave functions to uncover the evolution of resonance parameters until they cross the upper Aq+(N=2) threshold, and a complex scaling method to analyze the survival of these Feshbach resonances across the threshold, which eventually makes them behave as shape resonances.
    No preview · Article · Apr 2014 · Journal of Physics Conference Series
  • C M Granados-Castro · J L Sanz-Vicario
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    ABSTRACT: We study the resonant photoionization of the Helium atom subject to ultrashort laser pulses by using a Feshbach formalism in the time domain. We solve the projected time-dependent Schrodinger equation in terms of a configuration interaction spectral method, with a total wave function expanded with configurations defined within bound-like ( ##IMG## [http://ej.iop.org/images/1742-6596/488/3/032023/jpconf14_488_032023_eqn001.gif] ) and scattering-like ( ##IMG## [http://ej.iop.org/images/1742-6596/488/3/032023/jpconf14_488_032023_eqn002.gif] ) halfspaces. The method allows for accurate descriptions of both the atomic structure (energy positions and widths) as well as for the resonant photodynamics using ultrashort laser pulses. Special attention is given to the temporal formation of Fano profiles in the one- and two-photon ionization cross sections.
    No preview · Conference Paper · Jul 2013
  • Andrés Felipe Ordóñez-Lasso · Juan Carlos Cardona · José Luis Sanz-Vicario
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    ABSTRACT: We have implemented a method based on the Feshbach formalism along with an explicitly correlated configuration interaction method to perform a systematic study on the behavior of resonance parameters (energies and lifetimes) of the autoionizing states of plasma-embedded He 1,3Se, 1,3Po, and 1,3De, as a function of the screening strength. In particular, we study the evolution of the lowest states in the series located below the He+(N=2) ionization threshold in the unscreened case. At variance with one-electron atoms (where shape resonance widths vary monotonically with the screening strength) the evolution of the Auger width with respect to screening is found to be different for each series represented by (K,T)A pseudoquantum numbers until resonances merge into the upper electronic continuum, when crossing the He+(2s) threshold. We conclude from our ab initio calculations that, although resonances pertaining to the same (K,T)A series share a similar tendency in their widths against the screening strength, general propensity rules for the robustness of lifetimes, based on the isomorphic series in the (K,T)A classification, cannot be established in plasma-embedded helium.
    No preview · Article · Jul 2013 · Physical Review A
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    ABSTRACT: Atomic autoionization following photoabsorption is a typical example of quantum interferences governed by electron-electron correlation. Coherence between direct photoionization and autoionization paths results in "Fano profiles", widely explored in atoms in the last 60 years. The advent of femto- and attosecond laser technology made time-resolved images of the delayed electron ejection in autoionization accessible, leading to the reemergence of such studies in atomic systems. The counterpart molecular phenomena show the richness, as well as the complexity, added by nuclear motion, which may proceed on similar time scales. However, Fano profiles are usually absent in measured molecular photoionization cross sections and an unequivocal parametrization of molecular autoionization signatures, similar to that introduced by Fano in atoms [U. Fano, Phys. Rev. 1961, 124, 1866] has not yet been achieved. In this work we introduce a simple semiclassical model that accounts for all the features observed in H2 photoionization and demonstrate that the interference structures observed in dissociative ionization spectra are almost exclusively due to the phase accumulated in the nuclear motion. Furthermore, we show that the temporal build-up of these structures in the energy-differential cross sections is also determined by nuclear motion. We validate our models by comparing with full-dimensional ab initio calculations solving the time-dependent Schrödinger equation.
    No preview · Article · May 2013 · ChemPhysChem
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    C. M. Granados-Castro · J. L. Sanz-Vicario
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    ABSTRACT: (IOP Select 2013 - Also LabTalk available) We study the photoionization and autoionization of Helium atom subject to ultrashort laser pulses by using a Feshbach formalism in the time domain. We solve the time-dependent Schr\"odinger equation in terms of a configuration interaction (CI) spectral method, in which the total wavefunction is expanded with configurations defined within bound-like ($\mathcal{Q}$) and scattering-like ($\mathcal{P}$) halfspaces. The method allowsone to provide accurate descriptions of both the atomic structure (energy positions and widths) and the photodynamics. We illustrate our approach by i) calculating the time-resolved one-photon ionization below the He$^+$ ($n$=2) ionization threshold, from $1^1S^e$ and $2 ^1P^o$ initial states, then reaching the lowest autoionizing states of $^1S^e$, $^1P^o$ and $^1D^e$ final symmetries ii) studing the temporal formation of the Fano profile of $^1P^o$ resonances and iii) showing its performance in obtaining the perturbative long-time limit of one- and two-photon ionization cross sections using ultrashort laser pulses following a recently developed procedure in Phys. Rev. A, {\bf 77}, 032716 (2008).
    Full-text · Article · Mar 2013 · Journal of Physics B Atomic Molecular and Optical Physics
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    ABSTRACT: We study the dissociative photoionization of D2 by an attosecond pulse train (APT) in the presence of a near-infrared (IR) field. Strong oscillations in the D+ kinetic energy release spectrum with a half period of the optical cycle of the infrared field are observed and attributed to interferences between ionization pathways involving different harmonic orders of the APT due to the IR-induced coupling between the 1sσg and 2pσu ionization channels.
    No preview · Article · Nov 2012 · Journal of Physics Conference Series
  • C. M. Granados · J. L. Sanz-Vicario
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    ABSTRACT: A time dependent Feshbach method is implemented to study the correlated electron dynamics of He doubly excited states below the He+ (N=2) ionization threshold, using ultrashort laser pulses in XUV-pump IR-probe delay schemes.
    No preview · Article · Nov 2012 · Journal of Physics Conference Series
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    ABSTRACT: In this work, circular dichroism in H2 (D2) photoionization is studied in detail. We have selected several photon energies for a case study: 19 eV for which only direct ionization to the 1sσg ionization channel is present, 27 eV where autoionization of Q1 1Σ+u doubly excited states takes place, and 32.5 eV for which autoionization from Q1 and doubly excited states and direct ionization to 1sσg and 2pσu channels strongly interfere. The latter case shows clear evidence of different behavior of the photoionization against radiation helicity.
    No preview · Article · Nov 2012 · Journal of Physics Conference Series
  • J. C. Cardona · A. F. Ordoñez · J. L. Sanz-Vicario
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    ABSTRACT: We present a study on the 1,3Se, 1,3P° and 1,3 De He resonant states below the He+ (N = 2) threshold under the influence of a plasma environment, when the Debye screening length is varied. The interaction between all charged particles is modeled with Yukawa-like screened Coulomb potentials. We make use of the Feshbach projector method to characterize resonant states, implemented by using explicitly correlated CI-wave functions.
    No preview · Article · Oct 2012 · Journal of Physics Conference Series
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    ABSTRACT: We report experiments where hydrogen molecules were dissociatively ionized by an attosecond pulse train in the presence of a near-infrared field. Fragment ion yields from distinguishable ionization channels oscillate with a period that is half the optical cycle of the IR field. For molecules aligned parallel to the laser polarization axis, the oscillations are reproduced in two-electron quantum simulations, and can be explained in terms of an interference between ionization pathways that involve different harmonic orders and a laser-induced coupling between the 1sσ(g) and 2pσ(u) states of the molecular ion. This leads to a situation where the ionization probability is sensitive to the instantaneous polarization of the molecule by the IR electric field and demonstrates that we have probed the IR-induced electron dynamics with attosecond pulses.
    No preview · Article · Jul 2011 · Physical Review Letters
  • J. L. Sanz-Vicario · J. F. Pérez-Torres · F. Morales · E. Plésiat · F. Martín
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    ABSTRACT: The delayed autoionization of H2 doubly excited states into channels of different inversion symmetry gerade and ungerade is investigated by using pulses of attosecond duration (isolated or packed in trains), linearly polarized along the molecular axis. It has been shown in previous work, by using XUV laser pulses with durations of 4 fs or longer, that the molecular frame photoelectron angular distributions (MFPAD) associated with the dissociative channel H+ + H(nℓ) are not symmetric with respect to the inversion center of the molecule. In contrast, the MFPADs become symmetric for shorter fs pulses. Here we show that, although this is still the case for pulses of attosecond duration, the combination of two of these pulses with a controlled time delay may still lead to asymmetric MFPADs. From the analysis of the time evolution of the calculated MFPADs, we propose a way to elucidate autoionization lifetimes of molecular resonant states. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2462–2471, 2010
    No preview · Article · Nov 2010 · International Journal of Quantum Chemistry
  • Juan Carlos Cardona · José Luis Sanz-Vicario · Fernando Martín
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    ABSTRACT: Applications of the Feshbach formalism to systems of more than two active electrons are very scarce due to practical limitations in the construction of the projection operators P and Q that are inherent to the theory. As a consequence, most previous applications rely on the use of approximate quasiprojection operators, whose theoretical justification is not yet clear. In this work, an implementation of the Feshbach formalism for three-electron atoms is presented that includes all the ingredients of the original formalism. Energy positions and autoionization widths of the lowest 2Se, 2Po, and 2De autoionizing states of Li and Ne7+ have been evaluated. The results show that the use of quasiprojection operators is justified for the evaluation of resonant positions. However, for the 2Se states of Li, the use of quasiprojection operators can lead to errors in the autoionization widths of the order of 100%.
    No preview · Article · Aug 2010 · Physical Review A
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    ABSTRACT: Circular dichroism is a consequence of chirality. However, nonchiral molecules can also exhibit it when the measurement itself introduces chirality, e.g., when measuring molecular-frame photoelectron angular distributions. The few such experiments performed on homonuclear diatomic molecules show that, as expected, circular dichroism vanishes when the molecular-frame photoelectron angular distributions are integrated over the polar electron emission angle. Here we show that this is not the case in resonant dissociative ionization of H2 for photons of 30-35 eV, which is the consequence of the delayed ionization from molecular doubly excited states into ionic states of different inversion symmetry.
    No preview · Article · Jun 2010 · Physical Review Letters