17,451 research outputs found
Convergent close-coupling calculations of two-photon double ionization of helium
We apply the convergent close-coupling (CCC) formalism to the problem of
two-photon double ionization of helium. The electron-photon interaction is
treated perturbatively whereas the electron-electron interaction is included in
full. The integrated two-photon double ionization cross-section is
substantially below non-perturbative literature results. However, the pattern
of the angular correlation in the two-electron continuum is remarkably close to
the non-perturbative time-dependent close-coupling calculation of Hu {\em et
al} [J. Phys. {\bf B38}, L35 (2005)]Comment: 15 pages, 6 figure
Extremals for the Sobolev inequality on the seven-dimensional quaternionic Heisenberg group and the quaternionic contact Yamabe problem
Delay in atomic photoionization
We analyze the time delay between emission of photoelectrons from the outer
valence and sub-shells in noble gas atoms following absorption of an
attosecond XUV pulse. By solving the time dependent Schr\"odinger equation and
carefully examining the time evolution of the photoelectron wave packet, we
establish the apparent "time zero" when the photoelectron leaves the atom.
Various processes such as elastic scattering of the photoelectron on the parent
ion and many-electron correlation affect the quantum phase of the dipole
transition matrix element, the energy dependence of which defines the emission
timing. This qualitatively explains the time delay between photoemission from
the and sub-shells of Ne as determined experimentally by attosecond
streaking [{\em Science} {\bf 328}, 1658 (2010)]. However, with our extensive
numerical modeling, we were only able to account for less than a half of the
measured time delay of as. We argue that the XUV pulse alone cannot
produce such a large time delay and it is the streaking IR field that is most
likely responsible for this effect.Comment: 5 pages, 2 figure
On the use of the Kramers-Henneberger Hamiltonian in multi-photon ionization calculations
We employ the Kramers-Henneberger Hamiltonian for time-independent
calculations of multi-photon ionization of atoms with one and two electrons. As
compared to the electromagnetic interaction in the length and velocity gauges,
the presently employed Kramers-Henneberger gauge has an advantage of the dipole
matrix elements for the free-free electron transitions being finite and
well-defined quantities. This circumstance simplifies considerably the
computations and allows to obtain accurate results for the two-photon
ionization of realistic atomic systems.Comment: 16 pages, 1 figur
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