We present an extensive study of the static and dynamic properties of systems of spin-polarized tritium atoms. In particular, we calculate the two-body |F,m_F>=|0,0> s-wave scattering length and show that it can be manipulated via a Feshbach resonance at a field strength of about 870G. Such a resonance might be exploited to make and control a Bose-Einstein condensate of tritium in the |0,0> state. It is further shown that the quartet tritium trimer is the only bound hydrogen isotope and that its single vibrational bound state is a Borromean state. The ground state properties of larger spin-polarized tritium clusters are also presented and compared with those of helium clusters.
Data analysis of the next generation effective antineutrino mass measurement experiment KATRIN requires reliable knowledge of systematic corrections. In particular, the width of the daughter molecular ion excitation spectrum rovibrational band should be known with a better then 1% precision. Very precise ab initio quantum calculations exist, and we compare them with the well known tritium molecule parameters within the framework of a phenomenological model. The rovibrational band width with accuracy of a few percent is interpreted as a result of the zero-point atomic oscillation in the harmoni…
We report on the first ESR study of atomic hydrogen and tritium stabilized in a solid T$_{2}$ and T$_{2}$:H$_{2}$ matrices down to 70$\,$mK. The concentrations of T atoms in pure T$_{2}$ approached $2\times10^{20}$cm$^{-3}$ and record-high concentrations of H atoms $\sim1\times10^{20}$cm$^{-3}$ were reached in T$_{2}$:H$_{2}$ solid mixtures where a fraction of T atoms became converted into H due to the isotopic exchange reaction T+H$_2\rightarrow$TH+H. The maximum concentrations of unpaired T and H atoms was limited by their recombination which becomes enforced by efficient atomic diffusion du…
Cryogenic source of atomic tritium for neutrino-mass measurements and precision spectroscopy
University of Turku（图尔库大学）；Sorbonne Université（索邦大学）；ENS-PSL Université（巴黎文理研究大学）；Collège de France（法兰西公学院）；Institut Max von Laue - Paul Langevin（马克斯·冯·劳厄-保罗·朗之万研究所）；Marietta Blau Institute for Particle Physics, Austrian Academy of Sciences（奥地利科学院玛丽亚·布劳粒子物理研究所）；Institute for Particle Physics and Astrophysics, ETH（苏黎世联邦理工学院粒子物理与天体物理研究所）；Institute for Astroparticle Physics (IAP), Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院亚原子物理研究所）
Bound-state beta decay of tritium: Path to first observation and novel approach to direct neutrino mass measurement
Max-Planck-Institut für Kernphysik（马克斯·普朗克核物理研究所）；Institute for Astroparticle Physics, Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院天体粒子物理研究所）；AG Moderne Optik, Institut für Physik, Humboldt-Universität zu Berlin（柏林洪堡大学物理学院现代光学研究组）
We present a four-mode model that describes coherent photo-association (PA) in a double-well Bose-Einstein condensate, focusing on the $average$ molecular populations in certain parameters. Our numerical results predict an interesting strong-damping effect of molecular oscillations by controlling the particle tunnellings and PA light strength, which may provide a promising way for creating a stable molecular condensate via coherent PA in a magnetic double-well potential.
We demonstrate coherent one-color photoassociation of a Bose-Einstein condensate, which results in Rabi oscillations between atomic and molecular condensates. We attain atom-molecule Rabi frequencies that are comparable to decoherence rates by driving photoassociation of atoms in an $^{88}$Sr condensate to a weakly-bound level of the metastable $^{1}S_{0}+^{3}P_{1}$ molecular potential, which has a long lifetime and large Franck-Condon overlap integral with the ground scattering state. Transient shifts and broadenings of the excitation spectrum are clearly seen at short times, and they create …
The dynamics of a two-mode Bose-Einstein condensate trapped in a double-well potential results approximately in an effective Rabi oscillation regime of exchange of population between both wells for sufficiently strong overlap between the modes functions. Facing this system as a temporal atomic beam splitter we show that this regime is optimal for a nondestructive atom-number measurement allowing an atomic homodyne detection, thus yielding indirect relative phase information about one of the two-mode condensates.
Preparation of molecular quantum gas promises novel applications including quantum control of chemical reactions, precision measurements, quantum simulation and quantum information processing. Experimental preparation of colder and denser molecular samples, however, is frequently hindered by fast inelastic collisions that heat and deplete the population. Here we report the formation of two-dimensional Bose-Einstein condensates (BECs) of spinning $g-$wave molecules by inducing pairing interactions in an atomic condensate. The trap geometry and the low temperature of the molecules help reducing …
We report on the successful extension of production of Bose-Einstein Condensate (BEC) to rare species. Despite its low natural abundance of 0.13%, $^{168}$Yb is directly evaporatively cooled down to BEC. Our successful demonstration encourages attempts to obtain quantum gases of radioactive atoms, which extends the possibility of quantum many-body physics and precision measurement. Moreover, a stable binary mixture of $^{168}$Yb BEC and $^{174}$Yb BEC is successfully formed.
We present theoretical tools for predicting and reducing the effects of atomic interactions in Bose-Einstein condensate (BEC) interferometry experiments. To address mean-field shifts during free propagation, we derive a robust scaling solution that reduces the three-dimensional Gross-Pitaevskii equation to a set of three simple differential equations valid for any interaction strength. To model the other common components of a BEC interferometer---condensate splitting, manipulation, and recombination---we generalize the slowly-varying envelope reduction, providing both analytic handles and dra…
We experimentally investigate the formation of subradiant atomic momentum states in Bose-Einstein condensates inside a recoil resolving optical ring resonator according to the theoretical proposal of Cola, Bigerni, and Piovella. The atoms are pumped from the side with laser light that contains two frequency components. They resonantly drive cavity assisted Raman transitions between three discreet atomic momentum states. Within a few hundred microseconds, the system evolves into a stationary subradiant state. In this state, the condensate develops two density gratings suitable to diffract the t…
We propose a method of generating skyrmion vortices in a pair of Bose-Einstein condensates occupying two internal states of the same atom. We show that a variety of different periodic arrays of vortices may be prepared with an appropriate superposition of orthogonal standing electromagnetic waves inducing a coherent coupling between the two condensates.
We investigate the nonlinear dissipative coherence bifurcation and population dynamics of a two-component atomic Bose-Einstein condensate coupling with a continuum. The coupling between the two-component condensates and the continuum brings effective dissipations to the two-component condensates. The steady states and the coherence bifurcation depend on both dissipation and the nonlinear interaction between condensed atoms. The coherence among condensed atoms may be even enhanced by the effective dissipations. The combination of dissipation and nonlinearity allows one to control the switching …
We demonstrate nanometer-scale spatial control of inter-atomic interactions in a Bose-Einstein condensate of ytterbium(Yb). A pulsed optical standing wave, tuned near an optical Feshbach resonance varies the s-wave scattering length continuously across the standing wave pattern. The modulated mean-field energy with a spatial period of every 278 nm is monitored by a diffraction pattern in a time-of-flight image. We observe a wide scattering length control of up to 160 nm. The demonstrated spatial modulation of the scattering length proves that the high resolution control of atomic interactions …
Probabilties of formation of various hydrogenic species during the exothermic nuclear $(n,{}^3$He$;t,p)-$reaction of atomic helium-3 with slow neutrons are determined. In particular, we have found that the probability to form the tritium atom ${}^3$H in its ground state is $\approx$ 55.19287 %, while analogous probability to form the protium atom ${}^1$H is $\approx$ 1.02363 %. Analogous probabilities of formation of the negatively charged hydrogen ions, i.e. the ${}^3$H$^{-}$ and ${}^1$H$^{-}$ ions, in the nuclear $(n,{}^3$He$; t,p)-$reaction with slow neutrons, are $\approx$ 7.8680 % and $\a…
We study the macroscopic quantum tunneling, self-trapping phenomena in two weakly coupled Bose-Einstein condensates with periodically time-varying atomic scattering length. The resonances in the oscillations of the atomic populations are investigated. We consider oscillations in the cases of macroscopic quantum tunneling and the self-trapping regimes. The existence of chaotic oscillations in the relative atomic population due to overlaps between nonlinear resonances is showed. We derive the whisker-type map for the problem and obtain the estimate for the critical amplitude of modulations leadi…
A theoretical scheme for an experimental implementation involving bisolitonic matter waves from an attractive Bose-Einstein condensate, is considered within the framework of a non-perturbative approach to the associate Gross-Pitaevskii equation. The model consists of a single condensate subjected to an expulsive harmonic potential creating a double-condensate structure, and a gravitational potential that induces atomic exchanges between the two overlapping post condensates. Using a non-isospectral scattering transform method, exact expressions for the bright-matter-wave bisolitons are found in…
We show that nonlinear interactions induce both the Zeno and anti-Zeno effects in the generalised Bose-Josephson model (with the on-site interactions and the second-order tunneling) describing Bose-Einstein condensate in double-well trap subject to particle removal from one of the wells. We find that the on-site interactions induce \textit{only} the Zeno effect, which appears at long evolution times, whereas the second-order tunneling leads to a strong decay of the atomic population at short evolution times, reminiscent of the anti-Zeno effect, and destroys the nonlinear Zeno effect due to the…
Collective two-color photoassociation of a freely-interacting 87Rb Bose-Einstein condensate is theoretically examined, focusing on stimulated Raman adiabatic passage (STIRAP) from an atomic to a stable molecular condensate. In particular, Drummond et al. [Phys. Rev. A 65, 063619 (2002); cond-mat/0110578] have predicted that particle-particle interactions can limit the efficiency of collective atom-molecule STIRAP, and that optimizing the laser parameters can partially overcome this limitation. We suggest that the molecular conversion efficiency can be further improved by treating the initial c…
We experimentally and theoretically investigate the lowest-lying axial excitation of an atomic Bose-Einstein condensate in a cylindrical box trap. By tuning the atomic density, we observe how the nature of the mode changes from a single-particle excitation (in the low-density limit) to a sound wave (in the high-density limit). Throughout this crossover the measured mode frequency agrees with Bogoliubov theory. Using approximate low-energy models we show that the evolution of the mode frequency is directly related to the interaction-induced shape changes of the condensate and the excitation. Fi…
