Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session Z08: Atom-Atom/Molecule/Surface CollisionsRecordings Available
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Chair: Lee Liu, JILA Room: Salon 7/8 |
Friday, June 3, 2022 10:30AM - 10:42AM |
Z08.00001: Investigation of entangled spin state between two Rb85 atoms in an optical tweezer Poramaporn Ruksasakchai, Lucile Sanchez, Marvin Weyland, Scott Parkins, Stuart Szigeti, Ashton Bradley, Mikkel F Andersen Spin-changing collisions have been widely used to generate entanglement in many-body systems. They have also been utilized to entangle two q-bits in a zero temperature experiment. However, generating entanglement at a higher temperature may pave the way to the development of practical quantum technologies. Recent research shows that the spin-changing collisions of two thermal atoms initially prepared in the F=2, m=0 ground state lead to strong spin pair correlations between the magnetic sub-states m=+1 and m=-1. These correlations can be a classical mixture of the initial spin states and the entangled spin state. Here, we use hot spin-changing collisions to generate entanglement between two rubidium-85 atoms trapped in an optical tweezer. We investigate the generation of the entangled state by driving stimulated Raman transition between the two magnetic sub-states. The result shows that spin-changing collisions generate the entanglement. We measure the lifetime of the entanglement as this is an important characteristic for a further use in quantum applications. Moreover, we perform a Ramsey-type experiment to demonstrate that the generated entanglement can be employed to make an entanglement enhanced magnetic field measurement. To further improve the efficiency of the entanglement generation, the experimental parameters such as bias magnetic field, and depth of the optical tweezer can be optimized. |
Friday, June 3, 2022 10:42AM - 10:54AM |
Z08.00002: Comparison of two multiplexed portable cold atom vacuum standards Lucas Ehinger, Bishnu P Acharya, Daniel S Barker, James A Fedchack, Julia Scherschligt, Stephen P Eckel We compare the vacuum measured by two portable cold atom vacuum standards (pCAVS) developed at NIST. Each pCAVS converts the loss rate of atoms from a magnetic trap to a vacuum pressure using ab initio calculations of the quantum atom-molecule collision cross-section. Our pCAVS devices share the same laser system and atom number measurements are interlaced to allow both pCAVS to measure pressure concurrently. The two pCAVS together detected a leak on the order of 10−6 Pa L/s. After fixing the leak, the pCAVS measured a pressure of about 20 nPa with approximately 2% uncertainty. The two pCAVS agree within their uncertainties, even when swapping some of their component parts. The operation of the pCAVS was found to contaminate the vacuum slightly, leading to a pressure increase of approximately 1 nPa under normal operating conditions. With improved thermal management, we expect that the vacuum contamination can be decreased sufficiently to allow primary pressure measurements in the extreme-high-vacuum range (<10−10 Pa). The pCAVS promises to deliver accurate measurements of vacuum below 10−6 Pa a while suffering significantly less from systematics that plague Bayard-Alpert ionization gauges. |
Friday, June 3, 2022 10:54AM - 11:06AM |
Z08.00003: Fano profile detected in lower angular momentum states Jianing Han, Juliet Mitchell, Ian Baum Both Fano-profile and van der Waals interactions can provide asymmetrically broadened line shapes. However, the fundamental mechanisms are quite different. In this presentation, the similarities and differences will be discussed. In addition, Fano profile detected in lower angular momentum states, which is caused by the interference between lower angular momentum states and the multipole-multipole coupled continuum, will be demonstrated. |
Friday, June 3, 2022 11:06AM - 11:18AM |
Z08.00004: Ozone formation in ternary collisions: Theory and experiment reconciled Viatcheslav Kokoouline, Marjan Mirahmadi, Vladimir Tyuterev, Jesus Perez Rios In this work, we present a theoretical study on the primary mechanism of ozone formation in the stratosphere, i.e., O+O2+M with M=Ar. Our approach is based on a direct treatment of the three-body process through a classical trajectory method in hyperspherical coordinates, without using the two-step approximation via intermediate complexes. As a result, after computing thermally-averaged coefficients for temperatures 5-900 K, we find that most O3 molecules appear in weakly bound states, which are further quenched, leading to a good agreement with available experimental data for temperatures 100-900K. |
Friday, June 3, 2022 11:18AM - 11:30AM |
Z08.00005: Attempts to investigate RDEC for single-layer graphene impacted by F9,8+ ions* John A Tanis, Khushi Bhatt, Asghar Kayani, David La Mantia Radiative double-electron capture (RDEC) occurs when the capture of two electrons by an ion occurs simultaneous with the emission of a single photon. This process, fundamental in atomic collisions, is considered as the inverse of double photoionization by a single photon in ion-atom collisions. RDEC has been successfully studied with gas1 and thin-foil2 targets, and only recently studied for single-layer graphene targets.3 The preliminary RDEC results for 2.11 MeV/u F9,8+ ions on graphene indicated cross sections that were too large, approaching values found for thin-foil targets when the thickness of the graphene was about a hundred times smaller. In the present work we have repeated the RDEC measurements with single-layer graphene as well as identical targets that had no graphene on them. The work was done at WMU with the 6-MV tandem van de Graaff accelerator. Graphene (∼0.35 nm thick) was mounted on a silicon nitride grid (200 nm thick) consisting of ∼6400 holes of 2 µm diameter on a 200 µm thick substrate. A Si(Li) spectrometer placed at 90° to the beam detected the emitted x rays while the magnetically separated outgoing charged particles were counted using silicon surface barrier detectors. Co[JAT1] incidences between x [JAT2] rays and charge-changed particles were observed with event-mode acquisition. The new results point to significantly smaller cross sections than those seen earlier. Reasons for this difference will be explored. 1D. S. La Mantia et al. 2020, Phys. Rev. Lett. 124, 133401; 2D. S. La Mantia et al. 2020, Phys. Rev. A 102, 060801(R); 3D. S. La Mantia et al. 2021, ViCPEAC 2021, Book of Abstracts, p. 108. |
Friday, June 3, 2022 11:30AM - 11:42AM |
Z08.00006: Phase-shift locking and unlocking in resonant-exchange scattering Robin Cote Resonant exchange is an important process in many-body dynamics and transport phenomena (such as spin, charge, or excitation diffusion). The underlying dynamics is described by the resonant exchange cross section. We show that the s-wave scattering, generally thought to contribute mainly in the ultracold (or Wigner) regime, dictates the overall cross section (and rate coefficient) over a broad range of energies. We derive an analytical expression and explain its applicability high above the Wigner regime. In particular, we demonstrate its relationship to the classical capture (Langevin) cross section and apply it to resonant charge transfer, and explain the large variations found for different isotopes. We explain the behavior through a “locking” and gradual “unlocking” of phase shifts with increasing energy. We illustrate the agreement between our expression and the full quantum mechanical cross section using the case study of Yb ion-atom collisions. |
Friday, June 3, 2022 11:42AM - 11:54AM |
Z08.00007: Collision Strengths and Line Ratios for PII as a Biosignature in Exoplanets Kevin M Hoy, Sultana N Nahar, Anil K Pradhan Being the ``backbone'' element of DNA, Phosphorus is a key element in the search for life in the Universe. To aid in the future search for Phosphorus in star-forming regions and thereby in exoplanets, we have constructed a line ratios emission model for PII. This low ionization state is likely to exist in gaseous nebulae with stellar formation and in exoplanetary atmospheres if those atmospheres contain any significant amount of P. There are also 3 primary lines among the fine-structure 3s23p2 transitions in the PII emission spectrum that we are particularly interested in: 3P2→3P0 at 21 μm, 3P2→3P1 at 33 μm, and 3P1→3P0 at 60 μm. Collision strengths for these transitions have been newly calculated and compared the results of Tayal (2004). This level of ionization and especially useful lines make this specific ion especially useful in the search for DNA-based life in the universe. Our results have been found and verified against each other using two versions of the code SPECTRA: The original Fortran version, which has proven accurate and reliable, and a new, modernized C++ version that incorporates the process of electron-ion recombination in its calculations, further improving the code’s accuracy. |
Friday, June 3, 2022 11:54AM - 12:06PM |
Z08.00008: Using Atomic and Molecular Data to Model Biosignature Abundances in Exoplanetary Atmospheres Michael Rothman We are developing Geant4-EXOPlanets (G4-EXOP), a toolkit for modeling host-star radiation transmission through planetary atmospheric layers. G4-EXOP uses eclipse geometry, capturing light propagated through the exoplanetary atmosphere and analyzing it for biosignature abundances. G4-EXOP is based on Geant4, a Monte Carlo program package enabling modeling of radiation and particle transmission through matter. Our toolkit uses atomic and molecular data to generate emission and absorption spectra, enabling characterization of abundances from line strengths. We focus on atomic biosignatures (H, C, N, etc.) and molecules containing them (H2O, CO2, CH4, etc). Phosphorus is a focus as abundances in stellar systems are vital for DNA-based life. We calculate atomic transition data using SUPERSTRUCTURE and report results for P and C. We obtain molecular data from ExoMol and report predicted oscillator strengths for H2O and CO2. The results include thermal Doppler Broadening. G4-EXOP will be a toolkit for modeling host-star radiation transmission through exoplanet atmospheres to characterize biosignature abundances within observations. |
Friday, June 3, 2022 12:06PM - 12:18PM |
Z08.00009: Laser-assisted charge transfer in positronium collisions with protons and antiprotons Ilya I Fabrikant, Harindranath B Ambalampitiya, Joshua Stallbaumer We study the process of laser-assisted charge transfer in collisions of positronium atoms with protons (antiprotons) with formation of Rydberg hydrogen (antihydrogen) atoms |
Friday, June 3, 2022 12:18PM - 12:30PM |
Z08.00010: Theoretical prediction that oD2 spin-echo experiments can measure adsorbate diffusion Joshua T Cantin, Gil Alexandrowicz 3He spin-echo experiments have been used to study adsorbate diffusion, surface phonons, and surface phasons. |
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