Cooling by Spontaneous Decay of Highly Excited Antihydrogen Atoms in Magnetic Traps

Pohl, Thomas; Sadeghpour, H. R.; Nagata, Y.; Yamazaki, Y.

doi:10.1103/physrevlett.97.213001

Cited by 44 publications

(49 citation statements)

References 16 publications

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“…Blackbody radiation can therefore efficiently stimulate emission or absorption processes and, in some cases, even can be the primary source of decay. The influence of blackbody radiation on the behavior of Rydberg states is well known and has been extensively investigated experimentally and theoretically [2,[21][22][23][24][25][26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

“…These measurements are complementary to recent all-optical measurements of the lifetimes of selected nl Rydberg states following excitation of ultracold atoms in MOT, which reveal the decay of the initially prepared Rydberg states of Rb with principal quantum numbers in the range 30-40 by fluorescence, blackbody-radiation-induced and collisional processes [31] and to earlier studies of the influence of blackbody radiation, in particular ionization, on the lifetimes and other properties of Rydberg states of atoms (see, e.g., Refs. [21][22][23][24][25][26][27][28][29], and [2] and references therein) In an effort to understand how the different radiative or collisional processes affect the evolution of Rydberg atom population and induce losses of atoms and molecules from the traps, we have successively extended the initial deceleration and trapping experiments by (i) deflecting the Rydberg atoms and molecules from the beam axis before loading them into off-axis traps in order to suppress collisions with other atoms and molecules in the beam [36], (ii) installing successive thermal shields around the traps and thermalizing these shields to progressively lower temperatures, down to below 10 K, (iii) comparing the behavior of atomic and molecular Rydberg states in experiments carried out on H atoms and H 2 molecules [37], and (iv) trying to model the relevant radiative and collisional processes.…”

Section: Introductionmentioning

confidence: 99%

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Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Seiler¹,

Agner²,

Pillet³

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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Supersonic beams of hydrogen atoms, prepared selectively in Rydberg-Stark states of principal quantum number n in the range between 25 and 35, have been deflected by 90 ○ , decelerated and loaded into off-axis electric traps at initial densities of ≈ 10 6 atoms/cm −3 and translational temperatures of 150 mK. The ability to confine the atoms spatially was exploited to study their decay by radiative and collisional processes. The evolution of the population of trapped atoms was measured for several milliseconds in dependence of the principal quantum number of the initially prepared states, the initial Rydberg-atom density in the trap, and the temperature of the environment of the trap, which could be varied between 7.5 K and 300 K using a cryorefrigerator. At room temperature, the population of trapped Rydberg atoms was found to decay faster than expected on the basis of their natural lifetimes, primarily because of absorption and emission stimulated by the thermal radiation field. At the lowest temperatures investigated experimentally, the decay was found to be multiexponential, with an initial rate scaling as n −4 and corresponding closely to the natural lifetimes of the initially prepared Rydberg-Stark states. The decay rate was found to continually decrease over time and to reach an almost n-independent rate of more than (1 ms) −1 after 3 ms. To analyze the experimentally observed decay of the populations of trapped atoms, numerical simulations were performed which included all radiative processes, i.e., spontaneous emission as well as absorption and emission stimulated by the thermal radiation. These simulations, however, systematically underestimated the population of trapped atoms observed after several milliseconds by almost two orders of magnitude, although they reliably predicted the decay rates of the remaining atoms in the trap. The calculations revealed that the atoms that remain in the trap for the longest times have larger absolute values of the magnetic quantum number m than the optically prepared RydbergStark states, and this observation led to the conclusion that a much more efficient mechanism than a purely radiative one must exist to induce transitions to Rydberg-Stark states of higher m values. While searching for such a mechanism, we discovered that resonant dipole-dipole collisions between Rydberg atoms in the trap represent an extremely efficient way of inducing transitions to states of higher m values. The efficiency of the mechanism is a consequence of the almost perfectly linear nature of the Stark effect at the moderate field strengths used to trap the atoms, which permits cascades of transitions between entire networks of near-degenerate Rydberg-atom-pair states. To include such cascades of resonant dipole-dipole transitions in the numerical simulations, we have generalized the two-state Förster-type collision model used to describe resonant collisions in ultracold Rydberg gases to a multi-state situation. It is only when considering the combined effects of collisional and radiative pr...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Seiler¹,

Agner²,

Pillet³

et al. 2016

J. Phys. B: At. Mol. Opt. Phys.

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“…This is a consequence of Laplace's equation, which forbids local electrostatic extrema for two-and three-dimensional systems. However, an electric potential Φ that satisfies Laplace's equation, and provides a restorative force in theẑ direction, is 1 : 12) where V 0 is the applied potential, and d is the characteristic well length. The restorative, and therefore confining, force inẑ for a massive particle with charge q can be seen by examining the gradient of the potential, which acts as the force on the particle,…”

Section: Single Particle Confinementmentioning

confidence: 99%

“…Moreover, to assist spectroscopic efforts, there are a number of schemes to further cool and de-excite the antihydrogen atoms to the ground state [12][13][14].…”

Section: Precision Comparison Of the Properties Of Hydrogen And Antihmentioning

confidence: 99%

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Detection of Trapped Antihydrogen

Hydomako

2013

Springer Theses

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The ALPHA experiment is an international effort to produce, trap, and perform precision spectroscopic measurements on antihydrogen (the bound state of a positron and an antiproton). Based at the Antiproton Decelerator (AD) facility at CERN, the ALPHA experiment has recently magnetically confined antihydrogen atoms for the first time. A crucial element in the observation of trapped antihydrogen is ALPHA's silicon vertexing detector. This detector contains sixty silicon modules arranged in three concentric layers, and is able to determine the three-dimensional location of the annihilation of an antihydrogen atom by reconstructing the trajectories of the produced annihilation products.This dissertation focuses mainly on the methods used to reconstruct the annihilation location. Specifically, the software algorithms used to identify and extrapolate charged particle tracks are presented along with the routines used to estimate the annihilation location from the convergence of the identified tracks. It is shown that these methods can determine the annihilation location with a spatial resolution between about 0.6 to 0.8 cm (depending on the coordinate being measured). Furthermore, a robust analysis to identify and reduce cosmic ray background events is described. The cosmic ray background can obscure the trapped antihydrogen signal, and its suppression leads to a significant increase in the annihilation detection sensitivity. The background suppression analysis involves examining the reconstructed detector event based on several selection criteria, including: the number of charged particle tracks, the radial vertex position, and a fit of a straight line to the event hit positions. By carefully optimizing these criteria, (99.54 ± 0.02)% of cosmic ray events are rejected, while (64.4 ± 0.1)% of antihydrogen annihilation events are retained. Finally, the experimental results demonstrating the first-ever magnetic confinement of antihydrogen atoms are presented. These results rely heavily on the silicon i detector, and as such, the role of the annihilation vertex reconstruction is emphasized.

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CPT symmetry tests with cold and antihydrogen

Yamazaki

Ulmer

2013

Annalen der Physik

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Precision comparisons of the properties of particles and their corresponding antiparticles are highly relevant because the Standard Model of elementary particle physics, a local, Lorentz-invariant field theory, is necessarily symmetric with respect to the combined CPT operation. This symmetry defines exact equality between the fundamental properties of particles and their anti-images. Any measured and confirmed violation constitutes a significant challenge to the Standard Model. Recent results of different CPT-tests are summarized, with emphasis to the high-precision measurement of the magnetic moment of the proton and the antiproton, as well as the precision investigation of antihydrogen ground state hyperfine splitting.

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Cooling by Spontaneous Decay of Highly Excited Antihydrogen Atoms in Magnetic Traps

Cited by 44 publications

References 16 publications

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Radiative and collisional processes in translationally cold samples of hydrogen Rydberg atoms studied in an electrostatic trap

Detection of Trapped Antihydrogen

CPT symmetry tests with cold and antihydrogen

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