Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session U4: Spectroscopy |
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Chair: Marianna Safronova, University of Delaware Room: 204 |
Friday, June 7, 2013 10:30AM - 10:42AM |
U4.00001: Hydrogen and fluorine migration in photo double ionization of 1,1-difluoroethylene (C$_{2}$H$_{2}$F$_{2})$ B. Gaire, J. Rist, F. Sturm, N. Gehrken, A. Belkacem, Th. Weber, B. Berry, M. Zohrabi, I. Ben-Itzhak, M. Keiling, A. Moradmand, A. Landers, M. Schoeffler, T. Jahnke, H. Sann, M. Kunitski, R. Doerner Dissociative and nondissociative ionization of 1,1-C$_{2}$H$_{2}$F$_{2}$ is studied with single photons of energies between 40 to 70 eV by employing the Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) method. We present the branching ratio of nondissociative and two-body dissociative ionization channels as a function of photon energy. The yield of nondissociative ionization decreases significantly with higher photon energies. We have observed the migration of hydrogen and fluorine ions in some of the two-body dissociative ionization channels. The small yield of the H$_{2}^{+}+$C$_{2}$F$_{2}^{+}$ production indicates some interesting mechanisms for the formation of H$_{2}$ molecules. [Preview Abstract] |
Friday, June 7, 2013 10:42AM - 10:54AM |
U4.00002: Adiabatic Generation of Langmuir Trojan States in Helium Atom Matt Kalinski We propose the generation of the recently discovered Langmuir Trojan states [1] in helium atom by the adiabatic sequence of electric, magnetic and electromagnetic fields turn-ons. First the Trojan wavepacket is generated from one electron originally in the circular state leaving the $He^+$ ion core by the adiabatic rapid passage during Zener tunneling. Next, the plane of its circular motion is adiabatically shifted by the static Stark field turn on parallel to the magnetic field and than the second Trojan wavepacket from Helium $He^+$ ion is generated but to much smaller off resonant orbit not much to influence the first one. Later the ``two color'' CP field is adiabatically adjusted by the frequency chirping to one frequency while turning off the symmetry breaking electric Stark field and turning on the magnetic field to stabilize the orbits at the same time. Numerical simulations using the time dependent Hartree method reducing the problem two Schr{\"o}dinger equations in three dimensions solved with the Fast Fourier Transform split-operator method are also presented.\\[4pt] [1] Matt Kalinski, Loren Hansen, and David Farrelly,``Nondispersive Two-Electron Wave Packets in a Helium Atom,'' Phys. Rev. 95, 103001. [Preview Abstract] |
Friday, June 7, 2013 10:54AM - 11:06AM |
U4.00003: Production of Low Energy Electrons in a Small Molecular Environment F.P. Sturm, B. Gaire, I. Bocharova, P. Braun, A. Belkacem, Th. Weber, W. Cao, I. Ben-Itzhak, J.B. Williams, A. Landers, R. Doerner Low energy electrons contribute significantly to radiation damage in biological matter by ionizing neighboring molecules and inducing DNA strand breaking. However, little is known about the correlated generation of electrons and the mechanisms of the subsequent electron-initiated processes in molecular environments or clusters at a microscopic level. Applying a 3d momentum imaging technique (COLTRIMS), we have investigated the single-photon double ionization of oxygen dimers in order to single out and distinguish between different and important radiationless mechanisms (ICD and TS1). Their evolution is studied as a function of the energy of the incident photon. Differential energy and angular distributions help to understand the contributions of these competing mechanisms. [Preview Abstract] |
Friday, June 7, 2013 11:06AM - 11:18AM |
U4.00004: Breakup of H$_2^+$ by photon impact Daniel Haxton The photoabsorption cross section of the ground rovibrational state of H$_2^+$ is vastly dominated by breakup, i.e. dissociative ionization and dissociative excitation. To this point the breakup cross section had not been calculated in a formally exact ab initio treatment (without any Born-Oppenheimer approximation). Here such calculations are presented; all terms in the exact nonrelativistic Hamiltonian are included along with an exact representation of outgoing flux. The breakup cross section is calculated directly and divided into contributions from dissociative excitation and dissociative ionization channels. Approximate expressions for dissociative ionization that are often used are compared to exact expressions, and the approximate expressions are shown to be remarkably accurate in some cases but deficient in others near onset. See arxiv:1301.0153. [Preview Abstract] |
Friday, June 7, 2013 11:18AM - 11:30AM |
U4.00005: Exploiting the Rotational Dynamics of Asymmetric Top Molecules to make Angle Resolved, Molecular Frame Ion Yield and High Harmonic Measurements Varun Makhija, Xiaoming Ren, Jan Tross, Sudipta Mondal, Anh-Thu Le, Carlos Trallero, Vinod Kumarappan We extract the angle-dependent ionization rate of ethylene in an intense femtosecond laser pulse from the rotational revivals of the yield of the singly-charged molecular ion. By fitting the measured delay-dependent ion yield to the molecular axis distribution calculated using a rigid rotor code for asymmetric top molecules, we show that the dependence of the ionization rate on two Euler angles can be on obtained. Additionally we explore the possibility of extracting molecular frame information from similar pump-probe measurements of high harmonic generation. [Preview Abstract] |
Friday, June 7, 2013 11:30AM - 11:42AM |
U4.00006: Numerical Simulations of Single Photon Double Ionization of the Helium Dimer Hongcheng Ni, Camilo Ruiz, Reinhard Dorner, Andreas Becker We study the energy exchange via electron correlation upon photon absorption over large distances in double photoionization of the helium dimer. Results of numerical simulations of the interaction of a planar helium dimer model with a short light pulse are found to be in good agreement with recent experimental data for the angular distribution of the emitted electron. The double ionization probability is closely related to that of the photoemission of an electron from one of the helium atoms along the internuclear axis. This provides direct evidence for the knockoff mechanism by which the photon energy is shared between the electrons over distances of several Angstroms in the dimer. Furthermore, our simulations are able to visualize the knockoff process as a function of time. [Preview Abstract] |
Friday, June 7, 2013 11:42AM - 11:54AM |
U4.00007: Fully differential single-photon double ionization of neon and argon Frank L. Yip, Fernando Martin, Thomas N. Rescigno, C. William McCurdy Double photoionization of neon and argon differ significantly from helium in that three different final state couplings of the residual double ion ($^1S$, $^1D$, and $^3P$) are possible and greatly impact the observed angular distributions, but the multi-electron nature of such targets makes \emph{ab initio} theoretical treatments of this correlated process a challenge. Triply differential cross sections (TDCS) have been calculated for single photon double ionization of these heavier rare gases at various photon energies by utilizing an expanded frozen-core treatment to represent the remaining $N-2$ target electrons of the residual ion. The resulting angular distributions are compared with and show significant agreement with existing experimental data. [Preview Abstract] |
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