Session 8 – ATTOSECOND DELAYS IN PHOTOIONIZATION

Chair: Kenneth Schafer, Louisiana State University, Baton Rouge, USA

#34, 15:30 – 16:00 Time delay anisotropy in photoelectron emission from the isotropic ground state of helium, S. HEUSER, Á. JIMÉNEZ-GALÁN , C. CIRELLI, M. SABBAR, R. BOGE, M. LUCCHINI, L. GALLMANN , I. IVANOV, A. KHEIFETS , M. DAHLSTRÖM , E. LINDROTH, L. ARGENTI, F. MARTÍN AND U. KELLER, We present angle-resolved photoemission time delays of electrons ionized from the 1s 2 spherically symmetric ground state of helium. The observation that the time delay depends on the electron emission direction is attributed to the interplay between different final quantum states, which become accessible once two photons are involved in the photoionization process. This is a universal effect, which needs to be taken into account for any study dealing with photoionization dynamics.

#35, 16:00 – 16:15 Attosecond Delays in Resonant Photoionization, A. MAQUET , M. KOTUR, D. GUÉNOT, D. KROON, E. W. LARSEN, M. LOUISY, S. BENGTSSON, M. MIRANDA , J. MAURITSSON, C. L. ARNOLD, S. E. CANTON, M. GISSELBRECHT, A. L’HUILLIER, T. CARETTE , J. M. DAHLSTROM , E. LINDROTH, L. ARGENTI, Á. JIMÉNEZ-GALÁN, AND F. MARTÍN, We present the results of a study of time-delays in the photoionization of argon atoms in the combined presence of an IR laser field and of an attosecond pulse train of XUV harmonics. The frequency of the harmonics was tuned with objective to scan a Fano resonance involving the 3s23p6 → 3s13p64p1 transition. The experimental results are modeled with the help of a theoretical treatment that accounts for the variations of the time-delays in the region close to the resonance.

#36, 16:15 – 16:30 Attoclock based on polarization-resolved THz detection, ZHIHUI LÜ, DONGWEN ZHANG, CHAO MENG, YINDONG HUANG, XIAOWEI WANG, ZENGXIU ZHAO, JIANMIN YUAN, Employing a novel polarizationresolved detection, we precisely measured the polarization of terahertz emission from ionized gases in two-color field composed of circular polarized fundamental beam and linear polarized second harmonic. It shows that the polarization of the THz emission rotates with the phase delay and forms an attoclock. The polarization angular deviations of THz emissions in different laser intensities and different atoms reveal the distinct tunneling time delays. The polarization-resolved THz detection can be used to study tunneling ionization.

#37, 16:30 – 16:45 Photoionization dynamics: Transition and scattering delays, J. CAILLAT, M. VACHER, R. GAILLAC, A. MAQUET AND R. TAÏEB, The advent of attosecond science, with main objectives to probe and control ultrafast dynamics in quantum systems, recently brought a fresh look on photoemission. This very fundamental process was indeed recently revisited in the time domain, in a series of pioneering experiments that were soon accompanied by an intense theoretical activity devoted to the interpretation of the reported “photoemission delays”. At the conference, we will present some contributions of our group to this topic, with a focus on the characterization of photoemission dynamics in terms of “scattering” and “transition” delays as evidenced in numerical experiments performed on simple model systems.

#38, 16:45 – 17:00 Strong-field tunneling ionization: from adiabatic to nonadiabatic, MIN LI, JI-WEI GENG, XUFEI SUN, YUN SHAO, YONGKAI DENG, CHENGYIN WU, LIANG-YOU PENG, QIHUANG GONG, AND YUNQUAN LIU, In this contribution, we will present the recent result about tunneling ionization. We perform a high-resolution measurement of the ellipticity-resolved momentum distributions from tunneling ionization of Ar atoms along the major and minor axis in strong elliptically polarized fields. We further present a self-consistent subcycle nonadiabatic strong-field tunneling theory and show that the electron initial conditions for positions and momenta after the tunneling are non–adiabatically intertwined with each other. Disentangling the effect of the long-range Coulomb potential from the laser field, we demonstrate that the momentum-time structure off the tunneling wave packet in strong laser fields can be imaged.