Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session C06: Photoionization, Applications, and General Concepts |
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Chair: James Colgan, LANL Room: 206 A |
Tuesday, June 6, 2023 10:45AM - 10:57AM |
C06.00001: Asymmetric electron emission patterns in H2 & D2 after VUV + NIR photoabsorption Spenser J Burrows, Itzik Ben-Itzhak, Benjamin Berry, Elio G Champenois, Reinhard Doerner, Jan Dvorak, Averell S Gatton, Wael Iskander, Kirk A Larsen, Guillaume M Laurent, Robert R Lucchese, William McCurdy, Daniel Metz, Thomas N Rescigno, Hendrik Sann, Travis Severt, Niranjan Shivaram, Daniel S Slaughter, Miriam Weller, Joshua B Williams, Thorsten Weber Using the COLTRIMS technique, we investigated the dissociation of vibrationally excited H2 and D2 molecules after 2-color (VUV + NIR) absorption. The Advanced Light Source synchrotron provided VUV radiation to photoionize H2 (D2), leaving H2+ (D2+) ions in specific vibrational states. A synchronized 1030-nm NIR 12 ps laser pulse then dissociated these ions at a controlled time delay. We report on electron emission in the molecular frame, retrieved from the recoil ion lab-frame momentum, and its dependance on the orientation of the VUV and NIR polarizations. For some vibrational states, we observed an asymmetric photoelectron angular distribution that depends on the VUV/IR time delay. This asymmetry could be related to photoelectron retroaction with the dissociating ion. |
Tuesday, June 6, 2023 10:57AM - 11:09AM |
C06.00002: Double K-shell Photoionization of Ne Thomas W Gorczyca, Steven T Manson, Shuai Li, Denis Ceolin, Renaud guillemin, Gilles Doumy, Linda Young, Donald A Walko, Ralph Püttner, Iyas Ismail, Oksana Travnikova, Dimitris Koulentianos, Maria Novella N Piancastelli, Marc Simon, Stephen Southworth Single photon double K-shell photoionization of Ne has been studied experimentally and theoretically over the energy range of 2.3 – 8.5 keV. In particular, the KK/K photoionization ratios have been determined. The experimental cross sections were obtained via measurements of hypersatellite x-ray emission and the theoretical cross sections were calculated using the R-matrix with pseudostates (RMPS) method for Ne8+. Agreement between experiment and theory was quite good, indicating that the 8 outer-shell electrons of the Ne atom do not play an important role in double K-shell ionization, although small discrepancies are noted. Scaling of the ratio with Z is also investigated. |
Tuesday, June 6, 2023 11:09AM - 11:21AM |
C06.00003: Probing electron correlation in ethylene molecule by direct photo double ionization Moniruzzaman Shaikh, Wael Iskandar, Sun Y Lee, Daniel S Slaughter, Thorsten Weber Direct photo double ionization (PDI) of an atom or molecule by a single photon is an ideal testbed for investigating electron-electron correlation. Previous experimental investigations on simple hydrogen molecules over 20 years ago demonstrated that highly differential cross sections such as the relative electron emission angle in the body fixed frame with respect to the polarization vector can be measured and reproduced by ab initio calculations. Applying this approach to a polyatomic molecule provides the opportunity to better understand the interplay between electronic correlations within the molecule. Here, we investigated the PDI of single ethylene molecules near the double ionization threshold, in order to unravel the fundamental physics of electron correlation in inter-shell and intra-shell dielectron emissions and the subsequent molecular dynamics. |
Tuesday, June 6, 2023 11:21AM - 11:33AM |
C06.00004: Evidence of Core Hole localization in Molecular Frame Photoelectron Distributions in Dichloroethylene Cynthia S Trevisan, Demitri Call, Joshua B Williams, Thorsten Weber, Vern Davis, Reinhard Dörner, Allen L Landers, ITZHAK BENITZHAK, Oleg Kostko, Daniel S Slaughter, C. William McCurdy, Robert R Lucchese, Thomas N Rescigno For the past few years, we have conducted theoretical and experimental searches for evidence of core hole localization in X-ray photoionization of molecules by determining molecular frame photoelectron angular dependences (MFPADs) and recoil frame photoelectron angular dependences (RFPADs). Results have ranged from unambiguous, in the case of CF4 F(1s), to less evident, as in the case of Cl(2p) ionization in CCl4, where calculations suggest that the observed RFPADs mostly match theory with the electron hole delocalized among the four equivalent Cl atoms. Recent experiments on 1,1 dichloroethylene (H2C2Cl2) show a contrasting result that suggests a second case of the visibility of strong core hole localization on one of a set of equivalent atoms in the MFPAD. Upon Auger decay following Cl(2p) ionization, one dissociation channel produces H+ + H+ + Cl+. Comparisons of the resulting MFPAD for unequal energy sharing between the protons with theoretical calculations suggest that in this case the electron hole is strongly localized on one Cl atom. We will present the results of this investigation that combines ab initio calculations using the Complex Kohn method and COLTRIMS experiments at the Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory. |
Tuesday, June 6, 2023 11:33AM - 11:45AM |
C06.00005: Fully differential double photoionization of Li2 molecule Frank L Yip, Robert R Lucchese, Thomas N Rescigno, C W McCurdy The angular- and energy-differential cross sections for single photon double ionization of diatomic Li2 are reported in the molecular frame; this represents a fully differential theoretical study of double ionization from a molecule with more than two electrons. In addition to being a many-electron molecular target possessing core electrons whose interactions influence the outgoing valence electrons, the symmetry of the overall initial and final states are analogous with the same process in H2, thus permitting a direct comparison of the body-frame angular distributions that result from double ionization from these two molecular targets. We also examine the nature of initial state correlation in a natural orbital expansion for which we also compare with H. The advance of ab initio methods described here to molecules with more than two electrons represents an important and necessary step towards being able to describe even the simplest many-electron molecular double photoionization event. |
Tuesday, June 6, 2023 11:45AM - 11:57AM |
C06.00006: Ab initio quantum scattering calculations for modeling collision-perturbed molecular spectra Hubert Jozwiak, Maciej Gancewski, Artur Olejnik, Adam Zadrozny, Piotr Wcislo Accurate description of collisional effects in shapes of optical resonances is crucial for a reliable interpretation of molecular spectra and reduction of systematic errors in atmospheric measurements. We present a theoretical description of the shape of molecular spectra based on quantum scattering calculations performed on ab initio potential energy surfaces. We investigate molecular systems important in the astrophysical context (HD-H2), relevant to studies of Earth’s atmosphere (CO-N2, O2-N2, CO-O2, HCl-O2) and ultra-accurate spectroscopy for fundamental studies (H2-H2 and D2-D2). We present computational tools developed in our group and we address the challenges in solving coupled-channels equations in diatom-diatom systems. We discuss the application of the results presented here to the construction of a new generation of line-by-line spectroscopic databases populated with collisional line-shape parameters calculated from first principles. |
Tuesday, June 6, 2023 11:57AM - 12:09PM |
C06.00007: Configuration-interaction perturbation theory of Pu II with adjustable parameters Igor M Savukov, James Colgan Pu II with seven valence electrons is very difficult for atomic calculations due to strong valence-valence and valence-core interactions requiring significant computation resources. Configuration-interaction many-body perturbation (CI-MPBT) approach with a spherically symmetric starting potential when seven valence electrons are removed requires a very large basis sets to achieve convergence of valence-valence CI, and hence it is quite impractical. Alternatively, we explored much more proper starting potential that incorporates six 5f electrons that approximate the valence interactions and used configuration-interaction perturbation theory (CI-PT) which is much more efficient than CI-MPBT. However, CI-PT approach was developed initially for ab initio calculations. We introduced adjustment parameters to improve agreement between experiment and theory. As the result, we achieved quite close agreement of 200 inverse cm for many levels. At the meeting we will present the latest calculations of energies and g-factors for a number of Pu II levels. |
Tuesday, June 6, 2023 12:09PM - 12:21PM |
C06.00008: Singlet potential energy surface for CaF-CaF reactions Hui Li, Dibyendu Sardar, Arthur Christianen, John L Bohn This work presents a full six-dimensional Born-Oppenheimer singlet potential energy surface for the reaction CaF + CaF → CaF2 + Ca through a combination of the multireference configuration interaction (MRCI) electronic structure calculation and machine learning techniques. We identify global and local minima in this four-body potential energy surface ss well as a reaction path that takes the system between them via a submerged barrier. Finally, we propose a plausible reaction path through which the reaction proceeds by a torsional movement, presenting a richer dynamics than the handoff mechanism of the SrF molecules. |
Tuesday, June 6, 2023 12:21PM - 12:33PM |
C06.00009: Highly-resolved Stark effect measurements of Rydberg states in nitric oxide Fabian Munkes, Patrick Kaspar, Philipp Neufeld, Alexander Trachtmann, Yannick Schellander, Lars Baumgärtner, Robert Löw, Tilman Pfau, Harald Kübler We demonstrate Stark effect measurements at room temperature of high-lying Rydberg states in nitric oxide. These states are generated using a three-photon continuous-wave excitation scheme. The readout is based on the detection of charged particles created by collisional ionization of Rydberg molecules. A theoretical discussion of the gained experimental results is given. |
Tuesday, June 6, 2023 12:33PM - 12:45PM |
C06.00010: Suppressing and tuning-out Raman transitions in multilevel alkali atoms via multi-path interference Arina Tashchilina, Logan W Cooke, Evgeny Moiseev, Joseph Lindon, Tian Ooi, Nicholas Milson, Lindsay J LeBlanc Raman coupling, a two-photon transition between ground states mediated through one or more excited states, is widely used in spectroscopy, laser cooling, and atomic state manipulation. Adiabatic elimination of the upper manifold, which results in an effective two level atom, is commonly used to determine the effective strength of the two photon transition; here we explore the limits of validity for this approach. In many cases, we find that for certain transition pathways, interferences significantly suppress, or even tune out, the transition strengths. |
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