Bulletin of the American Physical Society
42nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 56, Number 5
Monday–Friday, June 13–17, 2011; Atlanta, Georgia
Session J6: Attosecond Spectroscopy |
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Chair: Anthony Starace, University of Nebraska–Lincoln Room: A706 |
Wednesday, June 15, 2011 10:30AM - 11:00AM |
J6.00001: Theory of attosecond transient absorption Invited Speaker: Attosecond transient absorption spectroscopy is potentially a powerful tool for studying electron dynamics on an ultrafast time scale. We present a theoretical study of transient absorption and reshaping of extreme ultraviolet (xuv) pulses by atoms dressed with a moderately strong infrared (ir) laser field. We formulate the atomic response using a time-frequency approach based on the time-dependent dipole induced by the light fields. We study attosecond transient absorption in a macroscopic gas by incorporating the time-frequency approach into a solution of the coupled Maxwell-Schroedinger equations. [Preview Abstract] |
Wednesday, June 15, 2011 11:00AM - 11:30AM |
J6.00002: Attosecond Electron Interferometry Invited Speaker: Attosecond light pulses have the potential to resolve the ultrafast electron dynamics that govern basic properties of atoms, molecules, and solids. Here we present three different interferometric pump-probe methods aiming to access not only the temporal dynamics, but also state specific phase information after excitation/ionization using attosecond pulses. These pulses have intrinsically very broad coherent bandwidths and in order to obtain state specific information we need to achieve a spectral resolution much better than the inverse of the pulse duration. We do this using either a train of pulses, which corresponds to a frequency comb in the spectral domain, or a pair of pulses, analog to traditional Ramsey spectroscopy, with the difference that the pulses have different frequencies. In the three experiments we: 1) measure the intensity dependence of the 2s-3p transition energy in helium using resonant two-color two-photon ionization [1]; 2) characterize an excited electron wave packet in helium by interfering it with a known reference [2]; and 3) measure the difference in time delay between electrons emitted from different sub-shells in argon [3]. In all three cases the spectral resolution is obtained by repeating the experiment many times for different delays between the attosecond pump pulses and the infrared probe pulses. The spectral resolution is then given either by the number of attosecond pulses [1] and [3] or the inverse of the pump-probe delay [2], which can easily be two orders of magnitude better than the Fourier limit of the excitation pulse. \\[4pt] [1] M. Swoboda, \textit{et al.}, ``Phase Measurements of Resonant Two-Photon Ionization in Helium'', Phys. Rev. Lett. \textbf{104}, 103003 (2010) \\[0pt] [2] J. Mauritsson, \textit{et al.}, ``Attosecond Electron Spectroscopy Using a Novel Interferometric Pump-Probe Technique'', Phys. Rev. Lett. \textbf{105}, 053001 (2010) \\[0pt] [3] K. Kl\"{u}nder, \textit{et al.}, ``Probing Single-Photon Ionization on the Attosecond Time Scale'', http://arxiv.org/abs/1012.3863 [Preview Abstract] |
Wednesday, June 15, 2011 11:30AM - 12:00PM |
J6.00003: Attosecond resonance dynamics in XUV-pump IR-probe simulations Invited Speaker: Short lived resonance states play an important role in many atomic and molecular charge changing processes where they can act as crucial intermediate steps towards ionization or recombination. The recent advances in the generation of attosecond pulses open a way to study, and perhaps control, the population and decay of such states in the time domain. We have investigated these possibilities by simulating an experiment focussing the He$\left(n=2\right)$ ionization threshold. An attosecond XUV pulse excites a breathing metastable wave-packet, formed by a coherent superposition of doubly excited resonance states. When probed with an intense and short IR pulse, the breathing motion is reflected in asynchronous quantum beats in the yields of excited He$^+\left( 2s\right)$ and He$^+\left( 2p\right)$ ions, as functions of the time delay between the two pulses~[1]. XUV excitation to doubly excited states followed by ionization by the IR probe-pulse interfere with direct XUV ionization, resulting in prominent interference fringes in the photoelectron angular distribution. Encoded is not only the accumulated phase difference, but also the path to ionization through absorption of several IR photons. Such fringes has also been demonstrated experimentally in a pump probe experiment targeting the He$\left(n=1\right)$ threshold~[2], were the authors suggest a interferometric technique aiming for amplitude and phase characterization of the packet created by an attosecond pulse.\\[4pt] [1] Luca Argenti and Eva Lindroth, Phys. Rev. Lett. {\bf 105}, 053002 (2010)\\[0pt] [2] J. Mauritsson {\em et al.}, Phys. Rev. Lett. {\bf 105}, 053001 (2010) [Preview Abstract] |
Wednesday, June 15, 2011 12:00PM - 12:30PM |
J6.00004: Attosecond Spectroscopy Invited Speaker: Attosecond spectroscopy is enabled by the advent of intense ultrashort light pulses comprising merely a few wave cycles. Manipulating the hyperfast-varying electric field evolution of these pulses permits the manipulation and tracking of the atomic-scale motion of electrons. A striking implication of this ability is the generation and characterization of isolated attosecond pulses of extreme ultraviolet (XUV) light and their characterization. Spectroscopic techniques making use of the unprecedented temporal resolution that attosecond XUV pulses offer can track and control electron dynamics in the interior of atoms, molecules as well as in solids and provide insight in the evolution of ultrafast electronic population dynamics and related coherent processes. Attosecond technology in combination with conventional electron spectroscopy, dubbed ``attosecond streaking'' investigates the timing of photoemission and electronic transport processes on solid surfaces. The extension of transient absorption measurement schemes makes coherent electronic dynamics accessible and the effects that ultrastrong and --short laser electric fields exert on the electronic structure of matter and the band structure population dynamics. [Preview Abstract] |
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