Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session J09: Structure and Properties of Atoms, Ions, and Molecules |
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Chair: Dmitri Babikov, Marquette University Room: Wisconsin Center 103DE |
Wednesday, May 29, 2019 10:30AM - 10:42AM |
J09.00001: Theoretical study of the Cf$^{15+}$ and Cf$^{17+}$ ions to develop an optical clock Sergey Porsev, Ulyana Safronova, Marianna Safronova A recent experimental progress in cooling and trapping of highly charged ions (HCIs) using sympathetic cooling made HCIs accessible for high resolution spectroscopy and precision fundamental studies. Based on these achievements, we explore a possibility to develop optical clocks using transitions between the ground and a low-lying excited state in the Cf$^{15+}$ and Cf$^{17+}$ ions. Low-lying energy levels for these ions were calculated earlier in [1,2] and it was shown that certain transitions are extremely sensitive to hypothetical variation of the fine-structure constant. Using a high-accuracy relativistic method of calculation we systematically studied properties of these ions and analyzed a number of systematic effects (such as the electric quadrupole-, micromotion-, and Zeeman quadratic shifts of the clock transitions) that affect the accuracy and stability of the optical clock. We also calculated magnetic dipole hyperfine-structure constants of the clock states and the blackbody radiation shifts of the clock transitions. The results will be reported at the conference. [1] V.A. Dzuba, M.S. Safronova, U.I. Safronova, and V.V. Flambaum, Phys. Rev. A {\bf 92}, 060502(R) (2015); [2] J.C. Berengut, V.A. Dzuba, V.V. Flambaum, and A. Ong, Phys. Rev. Lett. {\bf 109}, 070. [Preview Abstract] |
Wednesday, May 29, 2019 10:42AM - 10:54AM |
J09.00002: Stimulated Raman Transitions for Measuring Collisional Shifts in Ground State Hyperfine Levels Krishna Myneni, Hongrok Chang, Frank Narducci, Peter Bertone We demonstrate the use of stimulated Raman transitions to measure collisional shifts in low density atomic vapor cells with rubidium-perturber mixtures, at perturber partial pressures of 0.01 to 100 Torr. Traditionally, optical-radio frequency (RF) double resonance has been used to measure the ground state hyperfine doublet spacing in alkali-metal vapor in the presence of buffer gases at known densities. Stimulated-resonance Raman interaction has also been used to measure hyperfine level spacing in the yttrium ion ($\mbox{Y}^{+}$) and to demonstrate stable oscillators by locking to a two-pulse Ramsey fringe. Instead of stimulated-resonance Raman interaction, we use far detuned Raman transitions with a pulse sequence similar to that used in light-pulse atom interferometry to make precision hyperfine interval measurements of ${}^{87}\mbox{Rb}$. This procedure does not use the Raman-induced fluorescence for the detection of resonance. The Raman pulse width(s) and detection pulse intensity are optimized for high signal to noise ratio in the resonance signal. We show data for Rb-Ne and Rb-Ar vapor cells, discuss the systematic errors posed by AC Stark shifts in the measured intervals, and how to zero these errors. [Preview Abstract] |
Wednesday, May 29, 2019 10:54AM - 11:06AM |
J09.00003: Simple expressions based on relativistic impulse approximation for obtaining accurate whole atom Compton Profiles from photon scattering doubly differential cross sections Larry LaJohn There is continuing interest in the measurement of and the theoretical calculations of the values for Compton profiles (CPs) due to their many applications. Since CPs can only be obtained by measurement of physical observables such as photon or electron scattering doubly differential cross sections (DDCS), the accuracy of their values depends partly on the validity of the formulas used to transform DDCS into CP. Here such expressions, to be referred to as RKJ, based on relativistic impulse approximation (RIA) were derived for all K, L, M and N subshell nonrelativistic hydrogenlike wavefunctions. The derivation was done such that much of the relativistic and screening factors cancel, while the relativistic kinematic factors are retained making it possible to obtain CP from DDCS to within a few percent error over at least 99{\%} of the electron momentum distribution range at any energy ($\omega )$ in which RIA is valid and for atoms having a nuclear charge as high as 100. Good results over limited regimes of scattering angle and $\omega $ were obtained from two simpler RKJ expressions, one derived from the zero photon scattering angle limit the other from the high energy limit of full RKJ expression. [Preview Abstract] |
Wednesday, May 29, 2019 11:06AM - 11:18AM |
J09.00004: Temperature and density controlled measurements of a non-universal Efimov state in \textsuperscript{39}K Michael Van de Graaff, Xin Xie, Roman Chapurin, Noah Schlossberger, Jared Popowski, Jose D'Incao, Paul Julienne, Jun Ye, Eric Cornell We perform measurements of the absolute location of the Efimov ground state $a_{-}$ near a Feshbach resonance in $^{39}$K. The peak location is measured by loss spectroscopy in low density clouds for temperatures from 20-500nk. The effects of temperature saturation on the resonance peak location $a_-$ and width $\eta$ are characterized and demonstrate that the peak emerges more clearly at lower temperatures, consistent with finite temperature theory. This is in contrast to a recent similar study\footnotemark which showed the resonance to be shifted and surpressed at lower temperatures. Only at higher densities nearer to degeneracy do we observe the anamolous effects described by\footnotemark[\value{footnote}]. An accurate scattering length map derived from the precise measurement of the accompanying Feshbach resonance permits the determination of $a_{-}/r_{vdW}=14.19(16)$, significantly deviating from the value 9.73 predicted by van der Waals universality. We further characterize the effects of the trimer state for positive scattering lengths by measuring both the atom-dimer decay rate and the three-body recombination rate for free atoms. \footnotetext{Wacker \emph{et al.} PRA 98. 052706 (2018)} [Preview Abstract] |
Wednesday, May 29, 2019 11:18AM - 11:30AM |
J09.00005: Construction and analysis of dimensionally reduced potential energy surface of S$_{\mathrm{4}}$ and its vibrational states Igor Gayday, Dmitri Babikov Electronic structure calculations are carried out for S$_{\mathrm{4}}$ molecule at the CCSD(T)-F12a/VTZ-F12 level of theory to map out its potential energy surface that possesses a double-well shape with low-energy barrier. Two degrees of freedom are considered, the distance $R$ and the angle $\alpha $ between two weakly-perturbed S$_{\mathrm{2}}$ dimers that form S$_{\mathrm{4}}$. The resultant PES was computed near the bottom of the covalent well exposing transition state barrier energy of about 690 cm$^{\mathrm{-1}}$. Vibrational states are computed on this 2D-surface and assigned quantum numbers based on their energies and shapes of wavefunctions. Two progressions of vibrational states are identified: a long progression that develop nodes along the ``channels'' on the surface, and a shorter progression of states that develop nodes across the ``channels''. Normal mode analysis indicates that these two modes in S$_{\mathrm{4}}$ represent a significant mixture of conventional bending and stretching motions. Frequencies of the modes, approximately 180 cm$^{\mathrm{-1}}$ and 420 cm$^{\mathrm{-1}}$, are in qualitative agreement with earlier \textit{ab initio} studies of S$_{\mathrm{4}}$, and with sparse experimental data. [Preview Abstract] |
Wednesday, May 29, 2019 11:30AM - 11:42AM |
J09.00006: Polarization dependence of ladder-type electromagnetically induced transparency in cesium atoms Chin-Chun Tsai, Te-Hsin Chen, Ching-Yuan Su, Thi Thuy Nguyen, He-Yi Hsu We present an experimental and theoretical study of Polarization dependence in a ladder-type electromagnetically induced transparency (EIT) of cesium atoms. The probe field, vertical polarization, is frequency locked at one of the dipole-allowed transitions of $6S_{1/2}\rightarrow6P_{3/2}$ and scanning the coupling field, horizontal polarization, to access the excited state $6P_{3/2}\rightarrow 8S_{1/2}$. The transmittance of the probe laser field is monitored while the EIT occurred. To simulation the observed spectrum, Optical Bloch equation, two-photon transition probability, and optical pumping with polarization dependence are concerned and constitute in the theoretical model. Optical pumping with polarization dependence providing the population redistributes in magnetic Zeeman sublevel is a pivotal factor for fitting the experimental data. Our theoretical model properly generates the EIT intensity and line profile to fit the measured EIT spectra for all the possible hyperfine transitions in the three-level system. [Preview Abstract] |
Wednesday, May 29, 2019 11:42AM - 11:54AM |
J09.00007: Electric dipole matrix elements for the $6p\ ^2P_J \rightarrow 7s\ ^2S_{1/2}$ transitions in atomic cesium George Toh, Amy Damitz, Nathan Glotzbach, Jonah Quirk, I. C. Stevenson, J. Choi, M. S. Safronova, D. S. Elliott We report a measurement of the ratio of electric dipole transition matrix elements of cesium for the $6p\,^2P_{1/2} \rightarrow 7s\,^2S_{1/2}$ and $6p\,^2P_{3/2} \rightarrow 7s\,^2S_{1/2}$ transitions. We determine this ratio of matrix elements through comparisons of two-color, two-photon excitation rates of the $7s\,^2S_{1/2}$ state using laser beams with polarizations parallel to one another vs.\ perpendicular to one another. Our result of $R \equiv \langle 7s\ ^2S_{1/2} || r || 6p\ ^2P_{3/2} \rangle / \langle 7s\ ^2S_{1/2} || r || 6p\ ^2P_{1/2} \rangle = 1.5272 \ (17)$ is in excellent agreement with a theoretical prediction of $R=1.5270 \ (27)$, and the accuracy of our experimental ratio is sufficiently high to differentiate between various theoretical approaches. To our knowledge, there are no prior experimental measurements of $R$. Combined with our recent measurement of the lifetime of the $7s\,^2S_{1/2}$ state, we determine reduced dipole matrix elements for $\langle 7s\ ^2S_{1/2} || r || 6p\ ^2P_{3/2} \rangle$ and $\langle 7s\ ^2S_{1/2} || r || 6p\ ^2P_{1/2} \rangle$. These matrix elements are also in excellent agreement with theoretical calculations. Measurements like these improve knowledge of Cs properties needed for parity violation studies and provide benchmark [Preview Abstract] |
Wednesday, May 29, 2019 11:54AM - 12:06PM |
J09.00008: Electron Emission and Angular Anisotropy following the Beta Decay of Helium-6 Eva Schulhoff, Aaron Bondy, Gordon Drake Probabilities for atomic electron excitation (shake-up) and ionization (shake-off) are studied following the beta-decay process $^6{\rm He} \rightarrow \,^6{\rm Li}^+ + {\rm e}^- + \bar{\nu}_e$, and in particular, recoil corrections to the shake-off probability are calculated within the sudden approximation. A pseudostate expansion method together with Stieltjes imaging is used to represent the complete two-electron spectrum of final $^6$Li$^+$, $^6$Li$^{++}$, and $^6$Li$^{3+}$ states. Previous results [1] for the $1s2s\;^3S_1$ state of $^6$He as the initial state are extended to include the $1s2p\;^3P$ state, and rotational anisotropies in the electron emission spectrum are discussed. A variety of sum rules, including a newly derived TRK oscillator strength sum rule for dipole recoil terms, provides tight constraints on the accuracy of the results. The results are compared with recent experiments [2].\newline [1] E. E. Schulhoff and G. W. F. Drake, Phys.\ Rev.\ A {\bf 92}, R050701 (2015).\newline [2] R. Hong et al., Phys.\ Rev.\ A {\bf 96}, 053411 (2017). [Preview Abstract] |
Wednesday, May 29, 2019 12:06PM - 12:18PM |
J09.00009: First-Principles Molecular Spectra of Air Mark Zammit, Jeffery Leiding Comprehensive and highly accurate rovibronic spectral measurements of air molecules are critical to the modeling of low-temperature plasmas and air in extreme conditions. However, with the lack of experimental data, first-principles approaches are key to generating complete molecular line lists. Here, we will discuss the methodology employed for the accurate calculation of molecular rovibronic states, and present emission and equation of state results for NO, which forms in significant abundance in air under extreme conditions. [Preview Abstract] |
Wednesday, May 29, 2019 12:18PM - 12:30PM |
J09.00010: Atomic-Lifetime-Timescale Development of Birefringence in an Ultracold Gas Jonathan Gilbert, Mark Watkins, Jacob Roberts For near-resonance light incident on an optically thick gas of atoms, the light is strongly absorbed leading to an opaque gas in steady state. However, when the light is turned on over a time shorter than the excited state lifetime of the atoms, the gas is nearly transparent, and a large fraction of the initial light intensity is transmitted through the gas. This initial light peak is known as an optical precursor. In the presence of a magnetic field, a gas of multi-level atoms becomes birefringent, and at short times the light undergoes a time-dependent polarization rotation. This time-dependent birefringence influences the initially transmitted light signal as the atoms emit radiation in response to the local driving field. We have performed measurements of the optical precursor and the time-dependent phase difference between orthogonal components of the transmitted electric field in an optically thick gas of ultracold $^{85}$Rb atoms in the presence of different magnetic field strengths. We have also developed a model based on the optical Bloch equations that includes the relevant magnetic sub-levels of the ground state and excited state to compare to our experimental measurements. [Preview Abstract] |
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