Sessions 5 – ATTOSECOND SPECTROSCOPY I

Chair: Marc Vrakking, MBI, Berlin, Germany

  • Thomas Pfeifer
  • Esben Witting Larsen
  • Katsuya Oguri
  • Emma Simpson
  • Luca Argenti

#19, 8:30 – 9:00 Controlling Electronic and Nuclear Optical Responses in Atoms from Attoseconds to Nanoseconds, from VUV to Hard-X-Rays, THOMAS PFEIFER, Lasers provide spatially and temporally coherent light allowing for a wide range of control over quantum processes. Controllability of intense light on the attosecond time scale allows to introduce artificial phase jumps into the natural quantummechanical phase evolution of states, enabling new transient states of matter, endowing completely new properties to atomic systems. Here, we discuss the manipulation of atomic spectra and the underlying physical mechanism, which can be turned into a metrology scheme for quantum holography of laser-controlled bound electronic states. Based on the same principle, a novel laser-like coherent x-ray light source is envisaged, based on the time-domain control of nuclear resonances.

#20, 9:00 – 9:15 Free-induction Decay Induced by High-order Harmonics, ESBEN WITTING LARSEN, SAMUEL BENGTSSON, DAVID KROON, LARS RIPPE AND JOHAN MAURITSSON, We present an experimental study of controlled Free-induction Decay (FiD) in the extreme ultraviolet (XUV) regime. An attosecond pulse train is used to coherently promote argon to a superposition of the ground state ([Ne]3s23p6) and a series of excited states ([Ne]3s13p6np1), which are embedded in the [Ne]3s23p5 continuum. This superposition coherently emits light with the same directionality and divergence as the incoming XUV light. By applying a strong infrared probe pulse can either break the coherence, or control the direction and phase of the FiD.

#21, 9:15 – 9:30 Full determination of dipole response with inner shell using isolated attosecond pulse, HIROKI MASHIKOI, TOMOHIKO YAMAGUCHI, KATSUYA OGURI, AKIRA SUDA, AND HIDEKI GOTOH, We determined a dipole response with an inner shell using the combination of an isolated attosecond pulse (IAP) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). To fully characterize the dipole response, the decay time, dipole phase, and dipole oscillation have to be determined. We reconstruct the dipole response from the spectral interferogram, which is constructed with the IAP and the electromagnetic radiation generated from the dipole response in a neon atom.

#22, 9:30 – 9:45 Vector Response of a Dressed Continuum Probed by Transient Absorption, E.R. SIMPSON, S.E.E.HUTCHINSON, A.SANCHEZ-GONZALEZ, T.SIEGEL, Z.DIVEKI, M.RUBERTI, V.AVERBUKH, C.STRÜBER, L.MISEIKIS, D.AUSTIN AND J.P.MARANGOS, We measured the transient absorption of an attosecond pulse train (APT) by laser-dressed helium. We observed delay-dependent absorption features modulated at two and four times the frequency of the driving laser for harmonics in the APT both below and above the ionization limit for a range of dressing field intensities spanning 1012 Wcm-2 to 1014 Wcm-2. The absorption varied significantly with the angle between the linearly polarized fields. For the above threshold harmonics this behavior is reproduced by a full 3-D time-dependent Schrodinger equation (TDSE) single-atom theoretical calculation.

#23, 9:45 – 10:00 Modulation of Attosecond Beating in Resonant Two-Photon Ionization, L. ARGENTI, Á. JIMÉNEZ-GALÁN AND F. MARTÍN, We present a theoretical study of the photoelectron attosecond beating due to interference of two-photon transitions in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, both the phase and frequency of the sideband beating significantly vary with photon energy. Furthermore, the beating between two resonant paths persists even when the pump and probe pulses do not overlap, thus permitting to reconstruct nonholographically coherent metastable wave packets. We characterize these phenomena with an analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes.