Bulletin of the American Physical Society
41st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 55, Number 5
Tuesday–Saturday, May 25–29, 2010; Houston, Texas
Session X3: Strong Field Ionization |
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Chair: Alexei Sokolov, Texas A&M University Room: Imperial West |
Saturday, May 29, 2010 10:30AM - 10:42AM |
X3.00001: Strong field Multiphoton processes in the high-frequency limit Gilles Doumy, Christoph Roedig, Anthony DiChiara, Cosmin Blaga, Louis DiMauro, Pierre Agostini, Matthias Hoener, Li Fang, Norrah Berrah, Linda Young, Elliot Kanter, Bertold Kraessig, Stephen Southworth, Robin Santra, Stephen Pratt, Ryan Coffee, Phil Bucksbaum, James Cryan, James Glownia, Shambhu Ghimire, David Reis, Matthias Kuebel, Gerhard Paulus, John Bozek, Christoph Bostedt Last fall, the Linac Coherent Light Source at SLAC National Accelerator Laboratory has delivered users the world first X-ray free electron laser, allowing studying X-ray matter interaction at unprecedented photon flux. We will present the first attempts at observing multiphoton ionization in the X-ray regime, which have been realized by measuring both electron and ion spectra from the ionization of rare gases in the AMO end station. In addition to gaining insight into this new regime, our experiments also participated towards the characterization of this new light source (intensity, harmonic content{\ldots}). [Preview Abstract] |
Saturday, May 29, 2010 10:42AM - 10:54AM |
X3.00002: Experimental ionization of atomic hydrogen with few-cycle laser pulses D. Kielpinski, M.G. Pullen, W.C. Wallace, D.E. Laban, A.J. Palmer, R.T. Sang, G.F. Hanne, K. Bartschat, H.A. Quiney We report the first experiments on ionisation of atomic hydrogen using few-cycle laser pulses. Light from an amplified titanium:sapphire laser system is compressed in a hollow-core fiber to produce 6 fs, 100 $\mu$J pulses. These pulses are focused through a beam of atomic hydrogen at peak intensities up to $10^{15} {\mbox W}/{\mbox cm}^2$. The resulting photoelectrons are energetically filtered by an electrostatic repeller and the high-energy electrons are detected by a channeltron, yielding a measurement of the integrated electron energy spectrum above the repeller voltage. The data are compared to theoretical electron spectra computed by a matrix iteration method. [Preview Abstract] |
Saturday, May 29, 2010 10:54AM - 11:06AM |
X3.00003: Strong-field physics using TDCIS Phay Ho, Loren Greenman, Eugene Kamarchik, David Mazziotti, Robin Santra We present an implementation of the time-dependent configuration interaction singles (TDCIS) method for treating atomic strong-field processes. In order to remove the photoelectron wave packet at the end of the spatial grid, we add to the nonrelativistic many-electron Hamiltonian a radial complex absorbing potential (CAP). We determine orbitals by diagonalizing the sum of the Fock operator and the CAP using a radial pseudo-spectral grid combined with spherical harmonics. The CAP is chosen such that the occupied orbitals in the Hartree-Fock ground state remain unaffected. The virtual orbitals satisfy non-standard orthogonality relations, which affects the calculation of the dipole and Coulomb matrix elements required. We propagate the TDCIS equations of motion by second-order finite differencing in the interaction picture and transformation to the Schr\"{o}dinger picture. [Preview Abstract] |
Saturday, May 29, 2010 11:06AM - 11:18AM |
X3.00004: Quantum theory of recollisional (e, 2e) process in strong field nonsequential double ionization of helium Zhangjin Chen, Yaqiu Liang, C.D. Lin Based on the full quantal recollision model and field-free electron impact ionization theory, we calculated the momentum correlation spectra of the two outgoing electrons in strong field nonsequential double ionization (NSDI) of helium to compare with recent experiments. By analyzing the relative strength of binary vs recoil collisions exhibited in the photoelectron spectra, we confirmed that the observed finger- like structure in the correlation spectra is a consequence of Coulomb interaction between the two emitted electrons. Our result supports the recollision mechanism of strong field NSDI at the most fundamental level. [Preview Abstract] |
Saturday, May 29, 2010 11:18AM - 11:30AM |
X3.00005: Double Ionization of Helium in Combined Fields of Intense Near-infrared and VUV Laser Pulses Shaohao Chen, Andreas Becker Double ionization of He provides fundamental insights into the role of electron-electron correlation. The advent of sub-femtosecond laser technology with the generation of attosecond pulses in recent years has opened new perspectives towards the observation of the correlated electron dynamics on its natural time scale. In this work, we investigate the application of a VUV attosecond pulse to resolve sub-cycle correlated electron dynamics during the nonsequential double ionization process induced by an intense near-infrared laser field. To this end, we explore the relevant parameter regime (intensity, wavelength, pulse duration) of the VUV probe pulse by studying the ionization yields from scaled one-electron atoms. Then we solve the time-dependent Schrodinger equation based on a three-dimensional model for He atom, and study single and double ionization of the He atom induced by overlaping and nonoverlapping near-infrared and VUV pulses. The results calculated with and without the VUV pulse will be compared and discussed. [Preview Abstract] |
Saturday, May 29, 2010 11:30AM - 11:42AM |
X3.00006: Above-threshold ionization of Ca and Sr atoms Zengxiu Zhao, Jianmin Yuan, Yan Yin We investigate the above-threshold ionization of Alkaline earth atoms Ca and Sr by a strong laser field in the tunneling regime. Hartree-Fock potential is used in the simulation. Volkov propagater is applied in obtaining the high energy photoelectron spectra. The effect of the orthogonality between the dyanmic electron and the core electron orbitas, and the effect of laser-induced core polarization are examined. [Preview Abstract] |
Saturday, May 29, 2010 11:42AM - 11:54AM |
X3.00007: Electronic Correlation in strongly driven atomic and molecular systems Agapi Emmanouilidou In a quasiclassical framework we discuss the mechanisms of double ionization and the effects of electronic correlation during fragmentation of atomic and diatomic molecules when driven by intense and ultrashort laser pulses. [Preview Abstract] |
Saturday, May 29, 2010 11:54AM - 12:06PM |
X3.00008: An investigation of non-sequential double ionization with ultrafast long wavelength lasers Anthony D. DiChiara, Emily Sistrunk, Cosmin I. Blaga, Louis F. DiMauro, Pierre Agostini Long wavelength lasers allow access to tunneling ionization due to concomitantly large ponderomotive energies. Rescattering is known to occur when a tunnel ionized photoelectron is driven back by the field and collides with the parent ion. In this picture the wavelength of the laser field provides a `control knob' for rescattering since the cycle averaged kinetic energy of a free electron is quadratic with wavelength. We study the non-sequential ionization of Xenon and Krypton atoms as a function of wavelength (3.6, 2.0, 1.7, and 1.3 $\mu $m) and consequently return energy. For these laser parameters the maximum return energy provides an unexplored regime for non-sequential ionization. For example, at the longest wavelength studied the maximum classical return energy is over one order of magnitude larger than the ionization potential of the ion. The experiment is motivated by the extreme nature of the wavelength dependent return energies. We observe an enhancement of doubly ionized Krypton as compared to Xenon that cannot be understood by interpreting known impact ionization cross sections. [Preview Abstract] |
Saturday, May 29, 2010 12:06PM - 12:18PM |
X3.00009: Multiple ionization bursts from hydrogen molecular ion within a half-cycle of intense laser pulses Norio Takemoto, Andreas Becker Ionization dynamics of hydrogen molecular ion in intense near-infrared laser light is investigated on the attosecond time scale. In contrast to the quasi-static tunnel ionization picture which predicts that the ionization takes place predominantly around the peaks of the electric field, results of our numerical simulations indicate that there can be multiple bursts of ionization within a half cycle of the field oscillation. We show that these ionization bursts coincide with transient electron localization at one of the nuclei. By using a perturbation expansion of the Floquet states of a two state model, a simple formula has been derived to predict the instants of the electron localization and the ionization bursts from the vector potential of the laser light, the transition dipole between the ground and first-excited states, and the mixing angle of the two Floquet states. [Preview Abstract] |
Saturday, May 29, 2010 12:18PM - 12:30PM |
X3.00010: ABSTRACT WITHDRAWN |
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