Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session B9: Photoionization, Photodetachment and Photodissociation |
Hide Abstracts |
Chair: Nora Berrah, University of Connecticut Room: 556AB |
Tuesday, May 24, 2016 10:30AM - 10:42AM |
B9.00001: Fully differential single-photon double ionization of magnesium Frank L Yip, Thomas N Rescigno, C. William McCurdy The valence-shell double ionization of atomic magnesium is calculated using a grid-based representation of the $3s^2$ electron configuration in the presence of a fully-occupied frozen-core configuration. Atomic orbitals are constructed from an underlying finite element discrete variable representation (FEM-DVR) that facilitate accurate representation of the interaction between the inner shell electrons with those entering the continuum. Comparison between the similar processes of double ionization of the $ns^2$ atoms helium, beryllium and magnesium are presented to further illuminate the role of valence-shell electron correlation in atomic targets with analogous configurations and symmetries. Both a time-independent and time-dependent formalism for evaluating double ionization amplitudes is applied to these many-electron targets. Results are compared with recent theoretical calculations and experimental measurements. [Preview Abstract] |
Tuesday, May 24, 2016 10:42AM - 10:54AM |
B9.00002: Two-pathway interferences in photoelectron angular distributions induced by circularly polarized femto\-second pulses. Nicolas Douguet, Joel Venzke, Klaus Bartschat, Alexei N. Grum-Grzhimailo, Elena Gryzlova, Ekaterina Staroselskaya Following up on earlier work using linearly polarized radiation [1], we analyze the characteristics of atomic ionization produced by circularly polarized two-color femtosecond pulses. Two-pathway interferences between nonresonant one-photon and resonant two-photon ionization in the vicinity of an intermediate resonance are considered in detail for atomic hydrogen. Using circularly polarized radiation significantly increases the complexity of the problem, while opening up a rich field of possible further investigations [2]. The principal properties of the photoelectron angular distribution (PAD) are obtained by solving the time-dependent Schr\"{o}dinger equation and employing a second-order nonstationary perturbative approach. The dependence of the PAD on the intensities, helicities of the harmonics, pulse lengths, and carrier envelope phases is considered in detail. \par\noindent [1] A.N.~Grum-Grzhimailo, E.V.~Gryzlova, E.I.~Staroselskaya, J.~Venzke, and K.~Bartschat, Phys. Rev. A 91, 063418 (2015); erratum: Phys. Rev. A 93 (2016) 0199901(E). [2] N.~Douguet, A.N.~Grum-Grzhimailo, E.V.~Gryzlova, E.I.~Staroselskaya, J.~Venzke, and K.~Bartschat, Phys. Rev. A 93 (2016), in press. [Preview Abstract] |
Tuesday, May 24, 2016 10:54AM - 11:06AM |
B9.00003: Recoil effects due to electron shake-off following the beta decay of $^6$He Gordon W.F. Drake, Eva Schulhoff There are currently several experiments in progress to search for new physics beyond the Standard Model by high precision studies of angular correlations in the $\beta$ decay of the helium isotope $^6{\rm He}$ to form $^6{\rm Li} + e^- + \bar{\nu}_e$ [1,2]. After the $\beta$ decay process, the atomic electrons of $^6$Li$^+$ adjust to the sudden change of nuclear charge from 2 to 3. We calculate the probabilities for electron shake-up and shake-off, including recoil effects, by the use of a Stieltjes imaging representation of the final states. A variety of sum rules provides tight consistency checks on the accuracy of the results. Results obtained previously [3] indicate that there is a 7$\sigma$ disagreement between theory and experiment for the additional nuclear recoil induced by the emission of atomic shake-off electrons. This disagreement will be further studied, and the results extended to the $1s2p\;^3P$ and metastable $1s2s\;^3S$ states as initial states of $^6$He before $\beta$-decay.\\[5pt] [1] C. Couratin {\it et al.}, Phys.\ Rev.\ Lett.\ {\bf 108}, 243201 (2012).\\[0pt] [2] O. Naviliat-Cuncic and M. Gonzalez-Alonso, Ann.\ Phys.\ {\bf 525}, SI 600-619 (2013).\\[0pt] [3] Eva Schulhoff and G.W.F. Drake, Phys.\ Rev.\ A {\bf 92}, R050701 (2015). [Preview Abstract] |
Tuesday, May 24, 2016 11:06AM - 11:18AM |
B9.00004: The solar elemental abundances problem: Large enhancements in photoionization and bound-free opacity A. Pradhan, S. Nahar Aimed at solving the outstanding problem of solar opacity and radiation transport, we report substantial photoabsorption in the high-energy regime due to atomic core photo-excitations not heretofore considered. In an extensive R-Matrix calculations of unprecedented complexity for an important iron ion Fe~XVII, with a wave function expansion of 99 Fe~XVIII core states from $n\leq 4$ complexes (equivalent to 218 fine structure levels), we find: i) up to orders of magnitude enhancement in background photoionization cross sections, in addition to strongly peaked photo-excitation-of-core resonances not considered in current opacity models, and ii) demonstrate convergence with respect to successive core excitations. These findings may explain the "higher-than-predicted" monochromatic iron opacity measured recently at the Sandia Z-pinch fusion device at solar interior conditions [1]. The findings will also impact the total atomic photoabsorption and radiation transport in laboratory and astrophysical plasmas, such as UV emission from host stars of extra-solar planets.\\ 1. J. Bailey, et al., Nature, 517, 56 (2015).\\ Support: NSF, DOE, Ohio Supercomputer Center, Columbus, OH [Preview Abstract] |
Tuesday, May 24, 2016 11:18AM - 11:30AM |
B9.00005: An unambiguous signature in molecular frame photoelectron angular distributions of core hole localization in fluorine K-edge photoionization of CF$_4$ C. W. McCurdy, T. N. Rescigno, C. S. Trevisan, R. R. Lucchese Molecular Frame Photoelectron Angular Distributions (MFPADs) are calculated using the Complex Kohn variational method for core-hole ionization of the carbon and fluorines in CF$_4$ at photoelectron energies below 15 eV. The angular distributions for localized versus delocalized core-hole creation on the four equivalent fluorines are radically different. A strong propensity for the dissociation to take place via the mechanism $h\nu + \textrm{CF}_4 \rightarrow \textrm{CF}_4^+ + e^- \rightarrow \textrm{CF}_3^+ + \textrm{F}(1s^{-1}) \rightarrow \textrm{CF}_3^+ + F^+ + 2e^- $ in which a core excited neutral fluorine atom ionizes during or after dissociation creates the conditions for experimental observation of core hole localization. Comparison with recent unpublished experiments at the Advanced Light Source that measured the Recoil Frame Photoelectron Angular Distributions (averaged over CF$_3$ rotations around the recoil axis) for fluorine K-edge ionization gives unambiguous evidence that these experiments directly observed the creation of an almost completely localized core hole on the dissociating fluorine atom when the molecule was initially photoionized. [Preview Abstract] |
Tuesday, May 24, 2016 11:30AM - 11:42AM |
B9.00006: Direct Photo Double Ionization of Water and Subsequent Fragmentation D. Reedy, B. Gaire, A. Gatton, J. Sartor, B. Berry, M. Weller, T. Bauer, P. Burzynski, K. Henrichs, R. Dorner, J.B. Williams, Th. Weber, A.L. Landers We have measured and imaged the dissociation of water in the gas phase following direct double photoionization by a 57 eV photon. The dissociation left the dication in a range of several energetically available excited states. The momenta of the resulting dication fragments and photoelectrons were measured in coincidence with Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS). The different states of the dication result in marked differences in photoelectron energies, kinetic energy release, and bond angle at the time of the fragmentation, as well as leaving the neutral oxygen fragment in one of several indirectly observed excited states. [Preview Abstract] |
Tuesday, May 24, 2016 11:42AM - 11:54AM |
B9.00007: Photoionization of endohedral fullerenes using soft x-ray coincidence spectroscopy Razib Obaid, Hui Xiong, Utuq Ablikim, Sven Augustin, Kirsten Schnorr, Andrea Battistoni, Thomas Wolf, Ann Marie Carroll, Rene Bilodeau, Timur Osipov, Daniel Rolles, Nora Berrah Endohedral fullerenes are a model system to understand the reorganization dynamics of highly charged molecular systems with delocalized electronic clouds in the multiphoton excitation regime. Previous experiments at the Linac Coherent Light Source (LCLS) using free-electron laser (FEL) and ultrafast IR laser pulses studied this feature in Ho3N@C80. The question remains whether these dynamics can be studied in the site-specific single photo-ionization regime. Ho3N@C80 is particularly interesting since the inner molecule, Ho3N, is unstable in its natural form. The presence of the encapsulating cage, with the charge exchange characteristics of Holmium, stabilizes the whole molecule. In this study, we will present the charge fragmentation dynamics of this species in the single photoionization process of inner shell electrons (4d) of Holmium using the Advanced Light Source (ALS) at LBNL. Photoion-photoion correlation data, alongside with qualitative electron data will be presented. [Preview Abstract] |
Tuesday, May 24, 2016 11:54AM - 12:06PM |
B9.00008: Low-energy outer-shell photodetachment of the negative ion of boron. Kedong Wang, Oleg Zatsarinny, Klaus Bartschat The photodetachment of the negative ion of boron, B$\rm ^-(2s^22p^2)^3P$, was investigated by employing the $B$-spline \hbox{$R$-matrix} method [1] for photon energies ranging from threshold to 12~eV [2]. A multi-configuration Hartree-Fock method with non\-orthogonal, term-dependent orbitals was used to generate accurate initial bound-state and final continuum-state wave\-functions. The close-coupling expansion included all principal scattering channels for photo\-detachment from both the 2p and 2s orbitals. The resulting equation were solved using a parallelized version of the BSR computer code [3]. The calculated photo\-detachment cross sections are in good agreement with the available experimental data. Several prominent resonance features are predicted, thereby providing new challenges in the study of this highly correlated process. To classify the resonance structure, both the partial cross sections and the main contributions of the individual scattering channels are discussed. \par\noindent [1] O. Zatsarinny and K. Bartschat, J. Phys. B 46 (2013) 112001. \par\noindent [2] K. Wang, O. Zatsarinny, and K. Bartschat, EPJD (2016), in press. \par\noindent [3] O. Zatsarinny, Comp. Phys. Commun. 174 (2006) 272. [Preview Abstract] |
Tuesday, May 24, 2016 12:06PM - 12:18PM |
B9.00009: Formation of carbon chain molecular anions by radiative electron attachment and their destruction by photodetachment Marjan Khamesian, Nicolas Douguet, Maurice Raoult, Olivier Dulieu, Viatcheslav Kokoouline Several negative ions C$_n$H$^-$ ($n=4,6,8$), C$_n$N$^-$ ($n=1,3,5$) have been recently observed in the interstellar medium (ISM). A possible mechanism of formation is radiative electron attachment (REA). In this study we develop a first principle theoretical approach to study the REA and apply the approach to the formation of the negative molecular ions CN$^-$, C$_2$H$^-$, C$_3$N$^-$, C$_4$H$^-$, C$_5$N$^-$, C$_6$H$^-$, and C$_8$H$^-$. The theoretical approach is based on the UK R-matrix calculations. Cross sections and rate coefficients for formation of these ions by REA to the corresponding neutral radicals are calculated. There is no experimental data on REA of these ions. However, using a similar approach we have also calculated cross sections for photodetachment of the negative ions and compared the obtained results with available experimental data. The good agreement with photodetachment experimental data provides a confirmation that the REA cross sections obtained in this study is also reliable. [Preview Abstract] |
Tuesday, May 24, 2016 12:18PM - 12:30PM |
B9.00010: Implosive Interatomic Coulombic decay in the simplest molecular anion Chris H. Greene, Jesus Perez-Rios, Lyudmila Slipchenko Interatomic Coulombic decay (ICD) has been extensively studied in different systems: from diatomic systems such as He$_{2}$ up to more complex chemical systems with interest in biochemistry. Independently of the size and complexity of the system, the ICD process proposed involves the emission of an electron through exchange of a virtual photon. The present theoretical study investigates the ICD process in the helium hydride anion, which involves two final product states that can be produced through a Coulomb implosion following high energy ejection of a He 1s electron accompanied by excitation to He$^+(n=2)$. One of the subsequent decay channels is associated with the usual emission of a single electron, to produce a stable molecule: HeH$^+$, which can compete with the usual dissociated final state of the system. The second channel involves the emission of two electrons, leading to the usual Coulomb explosion of the final product ions He$^+(1s) + H+$. In addition, the process of formation of the helium hydride anion is analyzed in terms of the existing technology of ionic molecular beams and buffer gas cooling techniques. [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