Chair: Nora Berrah, University of Connecticut, USA

  • Fernando Martin
  • Judith Durá
  • Veit Stooß
  • Romain Géneaux
  • Giuseppe Sansone

#4, 10:30 – 11:00 Attosecond pump-probe schemes for the study of electron and nuclear dynamics in molecules, FERNANDO MARTÍN, The study of attosecond electron and nuclear dynamics by making use of pumpprobe schemes will be discussed from a theoretical perspective.

#5, 11:00 – 11:15 Control of multiphoton XUV ionization of argon by intense NIR fields, JUDITH DURÁ, MARTIN FLÖGEL, ARNAUD ROUZÉE, MARC J. J. VRAKKING, We present resonance-enhanced double ionization of Aratoms in intense XUV fields. A state of the art table-top source based on HHG that produces intense XUV fields is used. By monitoring the Ar 2+ yield as a function of the XUV pulse and an additional NIR pulse, we show that the formation of Ar 2+ ions proceeds via sequential two-photon XUV ionization resulting in the formation of singly charge excited Ar +* ions that are then ionized by the NIR laser pulse. We show that the population of the Ar+* excited cations can be controlled by a Stark-shift induced by the NIR pulse.

#6, 11:15 – 11:30 Observing the onset of inversion symmetry breaking of bound states in strong fewcycle laser fields, VEIT STOOß, ANDREAS KALDUN, CHRISTIAN OTT, ALEXANDER BLÄTTERMANN, THOMAS DING AND THOMAS PFEIFER, Electronic transitions and the states accessible to optical spectroscopy of atoms are governed by the symmetries of the corresponding atomic orbitals. When strong electric fields are applied to atoms, these symmetry properties change, resulting in modified selection rules and modifications in the characteristic absorption spectrum. Here, we explore the interaction of a strong few-cycle laser pulse with neutral helium and the characteristic signatures of parity symmetry breaking obtained in transient-absorption spectroscopy. We present experimental results for inversion symmetry breaking due to the DC-Stark effect caused by intense near-visible laser pulses. This approach can be used to study and control otherwise dipole-forbidden transitions with strong fields in the time domain.

#7, 11:30 – 11:45 Attosecond electron beams carrying orbital angular momentum, ROMAIN GÉNEAUX, ANTOINE CAMPER, THIERRY AUGUSTE AND THIERRY RUCHON, We measured the orbital angular momentum (OAM) of individual harmonics in a broad high harmonic (HHG) spectrum generated with an incoming IR beam carrying 1, 2 and 3 quanta of OAM. We established the conservation laws of OAM. We further used this light source to generate electron beams carrying a vortex and measured their attosecond time structure. This new secondary electronic source opens the way to new kind of spectroscopic applications, especially in solid state science.

#8, 11:45 – 12:00 Coherent control in the extreme ultraviolet spectral range using the Free Electron Laser FERMI@Elettra, P. CARPEGGIANI, G. SANSONE, M. REDUZZI, A. GRUM-GRZHIMAILO, E.V. GRYZLOVA, S.I.STRAKHOVA, K. BARTSCHAT, D. IABLONSKYI, Y. KUMAGAI, T. TAKANASHI, K. UEDA, A. FISCHER, F. STIENKEMEIER, T. MAZZA, M.MEYER, E. ALLARIA, C. CALLEGARI, R. CUCINI, G. DE NINNO, S. DI MITRI, B. DIVIACCO, E. FERRARI, P. FINETTI, D. GAUTHIER, L. GIANNESSI, N. MAHNE, G. PENCO, O. PLEKAN, L. RAIMONDI, P. REBERNIK, E. ROUSSEL, C. SVETINA, M. TROVÒ, M. ZANGRANDO, K. C. PRINCE, In this work we demonstrate for the first time the implementation of coherent control schemes in the extreme ultraviolet (XUV) spectral range. Using the combination of two XUV fields at frequency and 2, we demonstrate the control of the emission direction in the photoionization process of neon atoms. The fields were generated by the seeded FEL FERMI@Elettra, which, thanks to its unique characteristics of stability, spectral selectivity and coherence, allows for the control of the relative phase between the two components with a resolution less than 10 attoseconds.