[Todos] Seminario Conjunto en el DF - A. Abedi - E. Khosravi: Lunes 18/12, 14hs, Aula Seminario, 2do piso, Pab. I

[Augusto Roncaglia]

SEMINARIO CONJUNTO EN EL DEPARTAMENTO DE FÍSICA EXACTAS - UBA


                        En el Aula Seminario, 2do piso, Pab. I,

                        Lunes 18/12, 14hs:


1. *Correlated electron-nuclear dynamics*
   ALI ABEDI
   Universidad del Pais Vasco

2. *The exact potential driving the electron dynamics in enhanced
ionization of H2+- isotopes effects*
   ELHAM KHOSRAVI
   Universidad del Pais Vasco



*Correlated Electron-Nuclear Dynamics*

The coupling between electronic and nuclear motion plays an important role
in many fascinating phenomena, such as superconductivity, the process of
vision, as well as photo-synthesis. There are standard approximations such
as Ehrenfest dynamics or surface hopping that partially capture the
non-adiabatic effects. As a first step towards a full ab-initio treatment
of the coupled electron-nuclear system, we deduce an exact factorization of
the complete wavefunction into a purely nuclear part and a many-electron
wavefunction which parametrically depends on the nuclear configuration. We
derive formally exact equations of motion for the nuclear and electronic
wavefunctions [1-3]. These exact equations lead to a rigorous definition of
time-dependent potential energy surfaces (TDPES) as well as time-dependent
geometric phases. We analyze features of the TDPES in two topically
demanding situations:
molecules in strong fields [1-3] and splitting of a nuclear wave-packet at
avoided crossings [5] Born-Oppenheimer potential energy surfaces. In
addition, by studying a numerically exactly solvable model we demonstrate
that the molecular Berry phase and the corresponding non-analyticity in the
electronic Born-Oppenheimer wavefunction is, in general, not a true
topological feature of the exact solution of the full electron-nuclear
Schroedinger equation and only appear in the limit of infinite nuclear mass
[4].

Finally, we present a novel mixed quantum-classical approach [5] to the
coupled electron-nuclear dynamics based on the equations of motion for the
electronic and nuclear subsystems within the exact factorization framework.
The nuclear equation is a standard Schroedinger equation containing a TDPES
as well as a time-dependent vector potential. Starting from these
equations, the correct classical limit of the nuclear dynamics is worked
out by taking the classical limit of the exact time-dependent Schroedinger
equation satisfied by the nuclear wave function. The effect of the
time-dependent scalar and vector potentials, representing the exact
electronic back-reaction on the nuclear subsystem, is consistently derived
within the classical approximation. Using a model system, we examine the
performance of the proposed mixed quantum-classical scheme in comparison
with exact calculations, in the presence of strong non-adiabatic coupling
between the electronic and nuclear motion.

References:
[1] A. Abedi, N. T. Maitra, and E. K. U. Gross, Physical Review Letters 105
123002 (2010).
[2] A. Abedi, N. T. Maitra, and E. K. U. Gross, Journal of Chemical Physics
137 22A530 (2012)
[3] A. Abedi, F. Agostini, Y. Suzuki, E. K. U. Gross, Physical Review
Letters 110 263001 (2013).
[4] S. K. Min, A. Abedi, K. S. Kim, and E. K. U. Gross, Physical Review
Letters 113 263004 (2014).
[5] A. Abedi, F. Agostini, and E. K. U. Gross, Europhysics Letters 106
33001 (2014).




*The exact potential driving the electron dynamics in enhanced ionization
of H2+- isotopes effects*

The exact potential [1] driving the electron's dynamics [2] in enhanced
ionization of H2+ can have large contributions arising from dynamical
electron-
nuclear correlation, going beyond what any Coulombic-based model can
provide [3]. This potential is defined via the exact factorization of the
molecular
wavefunction that allows the construction of a Schrödinger equation for the
electronic system, in which the potential contains exactly the effect of
coupling
to the nuclear system and any external fields [1,2]. To investigate
nuclear-mass-
dependence in enhanced ionization, we study isotopologues of H2+ . We
decompose the exact potential into components that naturally arise from the
conditional wavefunction, and also into components arising from the marginal
electronic wavefunction, and compare the performance of propagation on these
different components as well as approximate potentials based on the quasi-
static or Hartree approximation with the exact propagation [4].

References:
[1]. A. Abedi, N. T. Maitra, and E. K. U. Gross, Phys. Rev. Lett. 105,
123002 (2010).
[2]. Y. Suzuki, A. Abedi, N. T. Maitra, K. Yamashita, and E. K. U. Gross, Phys.
Rev. A 89, 040501 (2014).
[3]. E. Khosravi, A. Abedi, and N. T. Maitra, Phys. Rev. Lett. 115, 263002
(2015)
[4]. E. Khosravi, A. Abedi, A. Rubio, N. T. Maitra, PCCP, 19 , 8269 (2017)
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