Physics of Atoms and Molecules

Atomic Physics

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Benchmarking theory with an improved measurement of the ionization and dissociation energies of H (1902.09471v1)

Nicolas Hölsch, Maximilian Beyer, Edcel J. Salumbides, Kjeld S. E. Eikema, Wim Ubachs, Christian Jungen, Frédéric Merkt

2019-02-25

The dissociation energy of H represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EF state and the 54p1 Rydberg state of H. When combined with previously determined intervals, this new measurement leads to an improved value of the dissociation energy of ortho-H that has, for the first time, reached a level of uncertainty that is three times smaller than the contribution of about 1 MHz resulting from the finite size of the proton. The new result of 35999.582834(11) cm is in remarkable agreement with the theoretical result of 35999.582820(26) cm obtained in calculations including high-order relativistic and quantum electrodynamics corrections, as reported in the companion article (M. Puchalski, J. Komasa, P. Czachorowski and K. Pachucki, submitted). This agreement resolves a recent discrepancy between experiment and theory that had hindered a possible use of the dissociation energy of H in the context of the current controversy on the charge radius of the proton.

Confinement of high- and low-field-seeking Rydberg atoms using time-varying inhomogeneous electric fields (1902.09392v1)

A. Deller, S. D. Hogan

2019-02-25

Helium atoms in high- and low-field-seeking Rydberg states with linear and quadratic Stark shifts have been confined in two dimensions and guided over a distance of 150 mm using time-varying inhomogeneous electric fields. This was achieved with an electrode structure composed of four parallel cylindrical rods to which voltages were applied to form oscillating and rotating saddle-point fields. These two modes of operation result in time-averaged pseudopotentials that confine samples in high- and low-field-seeking states about the axis of the device. The experimental data have been compared to the results of numerical particle trajectory calculations that include effects of blackbody radiation and electric field ionization. The results highlight important contributions from single-photon blackbody-induced transitions that cause large changes in the principal quantum number of the Rydberg atoms.

Phase protection of Fano-Feshbach resonances (1902.09262v1)

Alexander Blech, Yuval Shagam, Nicolas Hölsch, Prerna Paliwal, Wojciech Skomorowski, John W. Rosenberg, Natan Bibelnik, Oded Heber, Daniel M. Reich, Edvardas Narevicius, Christiane P. Koch

2019-02-25

Decay of bound states due to coupling with free particle states is a general phenomenon occurring at energy scales from MeV in nuclear physics to peV in ultracold atomic gases. Such a coupling gives rise to Fano-Feshbach resonances (FFR) that have become key to understanding and controlling interactions - in ultracold atomic gases, but also between quasiparticles such as microcavity polaritons. The energy positions of FFR were shown to follow quantum chaotic statistics. In contrast, lifetimes which are the fundamental property of a decaying state, have so far escaped a similarly comprehensive understanding. Here we show that a bound state, despite being resonantly coupled to a scattering state, becomes protected from decay whenever the relative phase is a multiple of . We observe this phenomenon by measuring lifetimes spanning four orders of magnitude for FFR of spin-orbit excited molecular ions with merged beam and electrostatic trap experiments. Our results provide a blueprint for identifying naturally long-lived states in a decaying quantum system.

Electronic level structure of in the range of the isomer energy (1902.09256v1)

David-Marcel Meier, Johannes Thielking, Przemysław Głowacki, Maksim V. Okhapkin, Robert A. Müller, Andrey Surzhykov, Ekkehard Peik

2019-02-25

Using resonant two-step laser excitation of trapped ions, we observe 166 previously unknown energy levels of even parity within the energy range from 7.8 to 9.8 eV and angular momenta from to . We also classify the high-lying levels observed in our earlier experiments by the total angular momentum and perform ab-initio calculations to compare their results with the observed level density. The observed levels can be relevant for the excitation or decay of the isomeric nuclear state which lies in this energy range. The high density of electronic levels promises a strongly enhanced electronic bridge excitation of the isomer in .

Near-100 % two-photon-like coincidence-visibility dip with classical light and the role of complementarity (1810.01297v2)

Simanraj Sadana, Debadrita Ghosh, Kaushik Joarder, A. Naga Lakshmi, Barry C. Sanders, Urbasi Sinha

2018-10-02

The Hong-Ou-Mandel effect is considered a signature of the quantumness of light, as the dip in coincidence probability using semi-classical theories has an upper bound of 50%. Here we show, theoretically and experimentally, that, with proper phase control of the signals, classical pulses can mimic a Hong-Ou-Mandel-like dip. We demonstrate a dip of 99.635 +/- 0.002% with classical microwave fields. Quantumness manifests in wave-particle complementarity of the two-photon state. We construct quantum and classical interferometers for the complementarity test and show that while the two-photon state shows wave-particle complementarity, the classical pulses do not.

Diffraction of a partial temporal coherent beam from a single-slit and a circular aperture (1806.04938v2)

E. Koushki, S. A. Alavi

2018-06-13

We generalize the notion of the Franhoufer diffraction from a single slit and a circular aperture to the case of partially temporal coherent and quasimonochromatic light. The problem is studied analytically and the effect of coherence length on the diffraction pattern is investigated. In this case the far-field distribution of the irradiance depends on the newly introduced parameter(decoherence parameter) which governs the deviation of the diffraction pattern from the usual one. The corrections due to temporal decoherency on the irradiance distribution in the far field is obtained. Numerical study of the effect of decoherence parameter on the Far-field diffraction pattern is performed. In the case of a single slit, there is no noticeable deviation in the central peak, but in the higher orders of diffraction, deviation become apparent. For circular apertures, as long as the decoherence parameter is greater than one , the beam decoherency affects the distribution profile and the first order diffraction pattern decreases and by increasing the decoherence parameter, the first order of diffraction pattern gradually disappears.

Pair fraction in a finite temperature Fermi gas on the BEC side of the BCS-BEC crossover (1803.10598v2)

Thomas Paintner, Daniel K. Hoffmann, Manuel Jäger, Wolfgang Limmer, Wladimir Schoch, Benjamin Deissler, Michele Pini, Pierbiagio Pieri, Giancarlo Calvanese Strinati, Cheng Chin, Johannes Hecker Denschlag

2018-03-28

We investigate pairing in a strongly interacting two-component Fermi gas with positive scattering length. In this regime, pairing occurs at temperatures above the superfluid critical temperature; unbound fermions and pairs coexist in thermal equilibrium. Measuring the total number of these fermion pairs in the gas we systematically investigate the phases in the sectors of pseudogap and preformed-pair. Our measurements quantitatively test predictions from two theoretical models. Interestingly, we find that already a model based on classical atom-molecule equilibrium describes our data quite well.

Quantitative optical spectroscopy of Rb vapour in the Voigt geometry in DC magnetic fields up to 0.4T (1810.01135v2)

J. Keaveney, F. S. Ponciano-Ojeda, S. M. Rieche, M. J. Raine, D. P. Hampshire, I. G. Hughes

2018-10-02

We present a detailed spectroscopic investigation of a thermal Rb atomic vapour in magnetic fields up to 0.4T in the Voigt geometry. We fit experimental spectra with our theoretical model \textit{ElecSus} and find excellent quantitative agreement, with RMS errors of %. We extract the magnetic field strength and the angle between the polarisation of the light and the magnetic field from the atomic signal and find excellent agreement to within % with a commercial Hall probe. Finally, we present an investigation of the relative sensitivity of this technique to variations in the field strength and angle with a view to enabling atom-based high-field vector magnetometry.

Dynamical enhancement of non-paraxial effects in electromagnetic field of a vortex electron (1902.08787v1)

Dmitry Karlovets

2019-02-23

A quantum state of an electron influences its electromagnetic field. If a spatial profile of the electron wave packet is not Gaussian, the particle may acquire additional intrinsic multipole moments, which alter its field, especially at small distances. Here the fields of a vortex electron with orbital angular momentum are obtained in a form of a multipole expansion with an electric quadrupole term kept by using the generalized (non-paraxial) Laguerre-Gaussian beams. The quadrupole contribution arises beyond a paraxial approximation, is linearly enhanced for highly twisted packets with , and can be important for the interactions of twisted beams with bulk matter and artificial structures. Moreover, this term results in an azimuthal asymmetry of the magnetic field in a rest frame of the electron, which is odd under time inversion and appears thanks to the spreading of the packet with time. Thus, somewhat contrary to physical intuition, the spreading may enhance non-paraxial phenomena. For the available electron beams, this asymmetry can in principle be reliably detected, which would be the first experimental evidence of a non-paraxial effect with the vortex electrons.

The open LPC Paul trap for precision measurements in beta decay (1810.09246v4)

P. Delahaye, G. Ban, M. Benali, D. Durand, X. Fabian, X. Fléchard, M. Herbane, E. Liénard, F. Mauger, A. Méry, Y. Merrer, O. Naviliat-Cuncic, G. Quéméner, B. M. Retailleau, D. Rodriguez, J. C. Thomas, P. Ujic

2018-10-18

The LPCTrap experiment uses an open Paul trap which was built to enable precision measurements in the beta decay of radioactive ions. The initial goal was the precise measurement of the beta-neutrino angular correlation coefficient in the decay of 6He. Its geometry results from a careful optimization of the harmonic potential created by cylindrical electrodes. It supersedes previously considered geometries that presented a smaller detection solid angle to the beta particle and the recoiling ion. We describe here the methods which were used for the potential optimization, and we present the measured performances in terms of trapping time, cloud size and temperature, and space charge related limits. The properties of the ion cloud at equilibrium are well reproduced by a simple numerical simulation using hard sphere collisions, which additionally gives insights on the trapping loss mechanism. The interpretation for the observed trapping liftetimes is further corroborated by a model recently developed for ion clouds in Paul traps. The open trap shall serve other projects. It is currently used for commissioning purpose in the TRAPSENSOR experiment and is also considered in tests of the Standard Model involving the beta decay of polarized Mg and Ca ion in the frame of the MORA experiment. The latter tests require in-trap polarization of the ions and further optimization of the trapping and detection setup. Based on the results of the simulations and of their interpretations given by the model, different improvements of the trapping setup are discussed.

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