International workshop on theory for attosecond quantum dynamics (IWTAQD) 9

June 17 -July 6, 2013

Diection to UEC
English, Japanese



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Participants (Bldg. E-6, Rms. 525, 527)

Oleg I. Tolstikhin Kurchatov Institute & MIPT
Adiabatic Theory
June 17 -July 6, 2013
Chiennan Liu Fu-jen University He dynamics under FEL June 19 - July 5, 2012
Yasuo Okajima Nara Inst Sci & Tech
Tunneling ionization

Yuto Toida
Nagoya Univ
Moleular dynamics
July 5, 2012
Kenichi Ishikawa U of Tokyo He dynamics June 20, 2013
Takeshi Sato U of Tokyo
Multielectron molecular dynamics
June 20, 2013
Hideki Ohmura
AIST Tunnel ionization of molecules
June 20, 2013
Michio Matsuzawa

June 20, 2013
Shinichi Watanabe
June 17 -July 6, 2013
Toru Morishita UEC
June 17 -July 6, 2013
Hsumin Hoang UEC 3-body break up June 17 -July 6, 2013
Masataka Ohmi UEC TDSE June 17 -July 6, 2013
Vinh Trinh Hoai UEC Tunnel ionizatoin June 17 -July 6, 2013
Vinh Pham Nguyen Thanh UEC Rescattering June 17 -July 6, 2013
Tomotake Yanakoshi
UEC Cold atoms June 17 -July 6, 2013
Osamu Ban
UEC Cold atoms June 17 -July 6, 2013
Shun Ohgoda
UEC Cold atoms June 17 -July 6, 2013
Satoshi Toge
UEC Cold atoms June 17 -July 6, 2013
Ryo Uno
UEC Cold atoms June 17 -July 6, 2013
Nanae Yokoyama
UEC Cold atoms June 17 -July 6, 2013
Haruhiko Alex Mizukoshi
UEC Attosec dynamics
June 17 -July 6, 2013
Asuka Hara
UEC Attosec dynamics June 17 -July 6, 2013

Seminar Program

June 20 (Thr)

Place: Bldg. East 6, Rm. 803

Chair : T. Morishita

SPEAKER: Yuto Toida, Nagoya U
TITLE: Ultrafast Photoelectron Spectroscopy of N2 Rydberg Wavepackets (in Japanese)
Recent developments of laser high-order harmonics generation have enabled us to employ ultrashort laser pulse as a probe for accessing atomic/molecular Rydberg states lying in EUV. In this work, we investigated Rydberg wavepackets dynamics of N2 using single-order harmonics at 80 nm and ultrashort laser pulse at 800 nm. Three extra peaks (v = 2 – 4) are identified in the photoelectron spectra in addition to the other two peaks (v = 0,1) observed in the conventional He I photoelectron spectrum. Each peak exhibits ultrafast decay characterized by double exponential function with ~ 0.3 and ~ 3 ps lifetime components. At a short time delay, periodic oscillation (~ 280 fs) was identified for v = 0, which is attributed to the motion of electron wavepakets in the Rydberg levels.
PDF file

SPEAKER: Trinh Hoai Vinh, UEC
TITLE: First-order correction terms in the weak-fi eld asymptotic theory of tunneling ionization
The weak- field asymptotic theory (WFAT) of tunneling ionization in a static electric field is developed to the next order in fi eld. The fi rst-order corrections to the ionization rate and transverse momentum distribution of the ionized electrons are derived. This extends the region of applicability of the WFAT at the quantitative level toward stronger fi elds, practically up to the boundary between tunneling and over-the-barrier regimes of ionization.
The results apply to any atom or molecule treated in the single-active-electron and frozen-nuclei approximations. The theory is illustrated by calculations for hydrogen and noble-gas atoms.

SPEAKER: Oleg I. Tolstikhin, National Research Center "Kurchatov Institute" & Moscow Institute of Physics and Technology, Moscow, Russia
TITLE:  Retardation effects and the Born-Oppenheimer approximation:
Theory of tunneling ionization of molecules revisited
We show that retardation in adjusting a bound electronic state to an instantaneous internu-
clear configuration caused by the finiteness of the electron’s velocity breaks the validity of the
Born-Oppenheimer (BO) approximation at large electron-nuclei distances. As a result, the BO
approximation in the theory of tunneling ionization of molecules breaks down at sufficiently weak
fields. We also show that to account for nuclear motion the weak-field asymptotic expansion for
the tunneling ionization rate must be restructured. The predictions for the rate using the BO
approximation and the asymptotic expansion are compared with numerical results for a model
treating both electronic and nuclear motions exactly.

SPEAKER:Hideki Ohumra, National Institute of Advanced industrial Science and Technology (AIST)
TITLE: Molecular tunneling ionization by multi-color phase-controlled laser fields
Intense (1012-1013 W/cm2) multi-color phase-controlled laser fields consisting of a fundamental light and the series of harmonics induce directionally asymmetric tunneling ionization and the resultant selective ionization of oriented molecules. It is demonstrated that selective ionization of oriented molecules induced by multi-color phase-controlled laser fields reflects the geometric structure of the highest occupied molecular orbital.

15:40-16:00 Break
SPEAKER: Chiennan Liu, Fu-Jen Catholic U, Taipei, Taiwan
TITLE: Two-electron dynamics in nonlinear double excitation of helium by intense ultrashort extreme-ultraviolet pulses
We present a theoretical study for multiphoton double excitation of He atoms exposed to an intense ultrashort extreme-ultraviolet (EUV) pulse, where the photon energy coincides with the transition energy from the ground state to a Rydberg state, by solving the time-dependent Schrödinger equation in the hyperspherical coordinates. Photoelectron spectra under the conditions comparable with a recent experiment [Hishikawa et al., Phys. Rev. Lett. 107 243003 (2011)] are calculated and analyzed. We identify the mechanism of the enhanced three-photon absorption probability which is more than one order of magnitude larger than that for the two-photon process in accordance with the experiment. The enhancement is attributed to a propensity rule for double excitation in a two-step mechanism, in which a one-photon absorption by one electron to a Rydberg state is followed by a two-photon absorption by the other electron to an excited orbital, while the first electron remains at nearly the same principle quantum number. Based on the time-dependent perturbation theory, the three-photon absorption probability exhibits peculiar cubic dependence on the pulse duration due to the propensity rule, in contrast to the linear dependence of the two-photon absorption probability. Thus a crossover between the two- and three-photon absorption probabilities takes place for sufficiently intense and long pulses. We also study the time evolution of a doubly excited two-electron wave packet created by an intense ultrashort EUV pulse efficiently using the same enhancement scheme, opening up the possibility of visualizing the correlated motion of two electrons in the time domain.

SPEAKER: Kenichi L Ishikawa, U. of Tokyo
TITLE: Two-photon ionization by femtosecond laser pulses
We discuss two-photon ionization, one of the most fundamental nonlinear processes. We first revisit the second-order time-dependent perturbation theory to clarify the contributions from resonant and nonresonant paths and their implication to photoelectron angular distribution. Then, we verify the theoretical prediction by the time-dependent Schrodinger equation (TDSE) simulations and measurements at the SCSS EUV-FEL. I may also discuss two-color two-photon ionization.

SPEAKER: Takeshi Sato, U. of Tokyo
TITLE: Time-dependent complete-active-space self-consistent-field method for multielectron dynamics in intense laser fields
Time-dependent complete-active-space self-consistent-field (TD-CASSCF) method is proposed for multielectron dynamics in intense laser fields. It introduces the concept of frozen-core (to model tightly bound electrons with no response to the field), dynamical-core (to model electrons tightly bound but responding to the field), and active (fully correlated to describe ionizing electrons) orbital subspaces, allowing compact yet accurate representation of ionization dynamics in many-electron systems.

Free discussion, Rm 529

Toru Morishita,UEC