Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session T5: Electron Dynamics in Atoms, Molecules, and Solids |
Hide Abstracts |
Chair: Wen Li, Wayne State University Room: Fairfield |
Friday, June 12, 2015 8:00AM - 8:12AM |
T5.00001: Core-shell resonant Auger-decay induced fragmentation of glycine molecule Li Fang, Hui Xiong, Timur Osipov, Vladimir Petrovic, Markus Guehre, Nora Berrah We investigated the fragmentation of glycine molecular ions induced by resonant Auger decay with synchrotron light source. We measured the charge distribution and the kinetic energies of various fragment ions with photon energies at the oxygen and the carbon 1s electron excitation resonance, as well as at photon energies above the K-edge of the oxygen and carbon atoms. We studied the fragmentation pathways using ion-ion coincidence measurement with a velocity map imaging spectrometer. We observed closure of certain fragmentation pathways at the on-resonance photon energy and the opening-up of certain fragmentation pathways by ionization of certain atomic sites. We will present that resonant Auger leads to unique dissociation patterns. [Preview Abstract] |
Friday, June 12, 2015 8:12AM - 8:24AM |
T5.00002: ABSTRACT WITHDRAWN |
Friday, June 12, 2015 8:24AM - 8:36AM |
T5.00003: Hybrid Gaussian-discrete variable representation for continuum electrons in molecules Frank L. Yip, C. William McCurdy, Thomas N. Rescigno A combined basis of analytic Gaussian functions and grid-based finite element discrete variable representation (FEM-DVR) with spherical harmonic expansion is specialized for description of continuum electron dynamics in the presence of electrons held fixed in core molecular orbitals. The applicability of this hybrid representation designed for general problems involving accurate determination of molecular continua wave functions is illustrated for photoionization of a second-row diatomic molecule, nitric oxide, NO. Accurate descriptions of such electron continuum dynamics are a necessary step towards analyzing correlated double continua photoejections. Examination of this hybrid method in comparison to a more computationally expensive pure grid-based single center expansion reveals several key advantages that by design make it attractive for describing processes involving one or more electrons moved to the continuum. [Preview Abstract] |
Friday, June 12, 2015 8:36AM - 8:48AM |
T5.00004: AM and FM in Molecular High-order Harmonic Generation XueBin Bian, Andre Bandrauk We theoretically studied the MHOHG from one-electron diatomic molecular ions in intense laser fields in a non-BO treatment to measure the influence of nuclear motion. Not only amplitude modulation (AM) [1-2], but also frequency modulation (FM) [3] encodes rich information of electron-nuclear correlation. It is found that the dissociation of molecules will lead to obvious redshifts in FM with intercycle dynamics in harmonic spectra. Usually the ionization rate of stable molecules at the equilibrium distance Re is very low. When the nuclear distance is bigger than Re, the ionization rate of the system increases rapidly. Consequently, most of the harmonic generation occurs on the falling part of laser pulses, where dI/dt \textless 0, leading to redshifts in MHOHG. This mechanism is confirmed by studying the isotope effect. The mechanism of FM in MHOHG is general, which can be directly applied to other light molecules if the ionization rate is sensitive to nuclear motion. It is hoped that this theoretical work will stimulate experimental studies in FM.\\[4pt] [1] M. Lein, Phys. Rev. Lett. 94, 053004 (2005).\\[0pt] [2] S. Baker, et al., Science 312, 424 (2006).\\[0pt] [3] X.-B. Bian and A. D. Bandrauk, Phys. Rev. Lett. 113, 193901 (2014). [Preview Abstract] |
Friday, June 12, 2015 8:48AM - 9:00AM |
T5.00005: High harmonic generation from Bloch electron in Solids Mengxi Wu, Shambhu Ghimire, David Reis, Kenneth Schafer, Mette Gaarde We study the generation of high harmonic radiation by Bloch electrons in a model solid driven by a strong mid-infrared laser field. We solve the single-electron time-dependent Schr\"odinger equation (TDSE) using a velocity-gauge method [New J. Phys. 15, 013006 (2013)]. The resulting harmonic spectrum exhibits a primary plateau due to the coupling of the valence band to the first conduction band, with a cutoff energy that scales linearly with field strength and laser wavelength. We also find a weaker second plateau due to coupling to higher-lying conduction bands, with a cutoff that is also approximately linear in the field strength. To facilitate the analysis of the time-frequency characteristics of the emitted harmonics, we also solve the TDSE in the Houston states [Phys. Rev. B 33, 5494 (1986)], which allows us to separate inter- and intra-band contributions to the current. We find that the inter- and intra-band contributions display very different time-frequency characteristics. We show that solutions in these two bases are equivalent under an unitary transformation but that, unlike the velocity gauge method, the Houston state treatment is numerically unstable when more than a few low lying energy bands are used. [Preview Abstract] |
Friday, June 12, 2015 9:00AM - 9:12AM |
T5.00006: Double Ionization of He by an Intense Elliptically-Polarized, Few-Cycle Attosecond Pulse Jean Marcel Ngoko Djiokap, Nikolai M. Manakov, Alexei V. Meremianin, Suxing Hu, Lars B. Madsen, Anthony F. Starace By solving the six-dimensional two-electron, time-dependent Schr\"{o}dinger equation for He interacting with an arbitrarily-polarized intense attosecond XUV pulse, we demonstrate numerically the control of He double ionization by means of the pulse polarization and its carrier-envelope phase (CEP).\footnote{J.M. Ngoko Djiokap \emph{et al.}, Phys.~Rev.~Lett. \textbf{113}, 223002 (2014).} Using perturbation theory (PT), we predict a new type of CEP-sensitive polarization asymmetry that is normally absent in single photon double ionization of He, but does occur for an elliptically-polarized, few-cycle attosecond XUV pulse. We call this new effect \emph{nonlinear dichroism},\footnote{Djiokap \textit{et al.}} which is sensitive not only to the ellipticity, peak intensity $I$, and temporal duration of the pulse, but also to the energy-sharing. This dichroic effect (i.e., the difference of the two-electron angular distributions for opposite helicities of the ionizing XUV pulse) originates from interference of first- and second-order PT amplitudes, allowing one to investigate and control S- and D-wave channels of the two-electron continuum. Nonlinear dichroism probes electron correlation on its natural timescale since it vanishes for long pulses. [Preview Abstract] |
Friday, June 12, 2015 9:12AM - 9:24AM |
T5.00007: Giant autoionization resonance enhancement and term-dependence of photoionization time delay in half-filled subshell atoms: the Mn atom Valeriy Dolmatov, Anatoli Kheifets, Steven Manson, Pranawa Deshmukh Time delay in photoelectron emission from atoms has become a hot topic of modern studies. To date, as far as we know, neither the significance of autoionization resonances in photoionization time delays has been established, nor features in time delays brought about by the configuration of open-shell atoms have been uncovered. To remedy the situation, we have studied the $3d$- and $4s$-photoionization time delays in the Mn(...$3d^{5}$$4s^{2}$, $^{6}S$) atom, which possesses a $3d^{5}$ half-filled subshell in its ground-state configuration, in the region of the well-known $3p \rightarrow 3d$ giant autoionization resonance ($\hbar\omega\approx 50$ eV, $\gamma \approx 2$ eV). The dramatic impact of the resonance on $3d$- and $4s$-time delay is demonstrated and the physics behind it is unraveled. Strong term-dependence of the $4s$-time delay [Mn $\rightarrow$ ${\rm Mn^{+}}(4s^{1},$$^{5}S)$ vs.~Mn $\rightarrow$ ${\rm Mn^{+}}(4s^{1},$$^{7}S)$] is discovered. The crucial importance of accounting for both the dominant $3d \rightarrow f$ and the (generally) smaller $3d \rightarrow p$ transitions in the calculation of the $3d$-photoinization time delay is established and explained. [Preview Abstract] |
Friday, June 12, 2015 9:24AM - 9:36AM |
T5.00008: Photoionization Cross Sections of P II: Theory \& Measurement Guillermo Hinojosa, E. Hernandez, A. Antillon, A. Morales-Mori, A. Juarez, A. Aguilar, A. Covington, D. Hanstorp, K. Chatkunch, O. Gonzalez, D. Macaluso, S. Nahar Features of photoionization of ground and many excited states (n$\leq$10) of P II are studied experimentally and theoretically. The ion is commonly formed in ECR ion sources and photionized. Photoionization cross sections of P II are needed for spectral analysis, but very little data are available. Experiment is done at Advanced Light Source at LLNL. Calculations are carried out in relativistic Breit-Pauli R-matrix method in close coupling approximation using a wave function of 18 levels of the core. Photoionization of the ground $3s^23p^2(^3P_0)$ and low lying exctied levels show low energy resonances with a broad feature indicating high probability of ionization. Theoretical results agree and identify the combined features of measurements. Comparison as well as other features, particularly of Seaton resonances due to photo-excitation of core, in the photoioniation cross sections will be illustrated. Photoionization cross sections of 475 levels will be reported. [Preview Abstract] |
Friday, June 12, 2015 9:36AM - 9:48AM |
T5.00009: Electron-ion Recombination and Photoionization of Ti I Sultana Nahar Ti I is commonly seen in the absorption spectra of red giant stars, cool M stars, Large Magellanic Cloud. They are easily ionizaed and form TiO. The amount of Ti locked in TiO can have direct effect on fluxes, spectral energy distributions and thus in determination of fundamental stellar parameters and abundances for these objects. Ionization fraction of the ions available requires both photoionization cross sections and recombination rate coefficients. Parameters for these processes are needed for spectral analysis for the objects. Ti I, a neutral atom of 22 electrons with open 3d shell, is a complex system due to strong electron-electron correlation effect and large number of bound states. The R-matrix calculations using a large wave function expansion reveals prominent resonant structures in the low energy region [1] indicating availability of photoionized ion Ti II to combine with oxygen. The resonant features will increase the opacity, as expected of astrophysical observation, and hence play important role in determination of abundances of elements. Level-specific and total recombination rates are being calculated under the Iron Project (AA 279, 298 1993). Features of recombination spectra with electron energy will also be presented.\\[4pt] [1] S.N. Nahar, New Ast. (in press 2015) [Preview Abstract] |
Friday, June 12, 2015 9:48AM - 10:00AM |
T5.00010: Imaging electronic motions in atoms by energy-resolved ultrafast electron diffraction Hua-Chieh Shao, Anthony F. Starace We present a general analysis of energy-resolved ultrafast electron diffraction for imaging target electronic motion and numerical simulations of time-resolved spectra of ultrafast electrons scattered from the breathing, wiggling, and hybrid modes of electronic motion in the H atom\footnote{H.-C.\,Shao and A.F.\,Starace, Phys.\,Rev.\,A \textbf{90}, 032710 (2014).}. We consider pump-probe processes in which a laser pulse creates a coherent superposition of target states that are probed by the electron pulses. Varying the pump-probe delay time, the delay-dependent scattering intensities record the ensuing electronic motions. The kinematics of the scattered electrons is fully resolved; both the scattering angles and the kinetic energies are measured. Therefore, besides the spatial and temporal information, the energy content of the electronic motions can be retrieved from the energy-resolved diffraction patterns, which provide unequivocal interpretations of the electronic motions. Because of this, we are able to explain the counterintuitive temporal behavior of the diffraction images, which show a quite different temporal behavior and little connection to the electron densities. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700