Antiprotonic helium and lithium with one or two electrons

High rotational states of¯p He and¯pLi atoms with one or two electrons are calculated in the Born-Oppenheimer approximation, with a precision which allows a systematic study of diabatic effects. The lifetimes of the relevant¯peα and¯pee Li states are in the μs range.     

Antiprotonic helium spectroscopy. Toward better than 10 digit precision

The recent progress in precision spectroscopy of the antiprotonic helium is outlined. It allows to claim that an accuracy achieved in the theoretical predictions for the ro-vibrational transition frequencies has relative uncertainty at a level of 10^?10.     

Effect of Wave-Function Mixing in Antiprotonic Helium

The effect of wave-function mixing in antiprotonic helium is discussed. This effect manifests itself in a considerable change of the Auger decay rate of long-lived states of ^3,4He e. Properties of short-lived states which influence the decay rate of long-lived ones are described. It is proposed to observe these short-lived states in a direct experiment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Optical-model analysis of exotic atom data: (II). Antiprotonic and sigma atoms

Data for antiprotonic and sigma atoms are fitted using a simple optical model with a potential proportional to the nuclear density. The potential strength can be related to the free hadron-nucleon scattering length using a model due to Deloff. A good overall representation of the data is also obtained with a black-sphere model.     

Sub-Doppler Two-Photon Laser Spectroscopy of Antiprotonic Helium and the Antiproton-to-Electron Mass Ratio

The ASACUSA collaboration of CERN has recently irradiated antiprotonic helium atoms with two counter-propagating laser beams. This excited some non-linear two-photon transitions of the antiproton at the deep UV wavelengths λ = 139.8–197.0 nm. The counterpropagating geometry of the laser beams reduced the thermal Doppler broadening of the observed resonances. Their narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3–5 parts in 10⁹. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23).     

High-Precision Calculation of the Fine and Hyperfine Structure Splittings of Antiprotonic Helium-3,4 Atoms

Hyperfine Interactions - In this work we explore electrochemical-polishing for thinning Fe-Mn samples. We set out by studying with CEMS and XCMS a sample approximately 1 mm thick of a bcc Fe-13.7...     

X-rays from antiprotonic helium in helium gas

X-ray transitions to the 4F, 3D, and 2P atomic levels of p?He have been observed with antiprotons stopped in He gas at 4 and 1.1 atm NT. The population by radiative transitions of the 3D level in gas Y_M(4atm) = (28±14)% and Y_M(1.1 atm) = (43±22)% exceeds by more than one order of magnitude that measured in liquid He. The annihilation width of the 3D level Γ^a_3D = 2.8±1.0 × 10^?3eV is determined from the ratio between the numbers of X-rays feeding and depopulating the 3D level. The strong-interaction shift of the 2P level ε(2P) = ?14±6 eV is obtained by inputting the $\text{p}\text{He}$ experimental X-ray yields into a cascade calculation, the results of which are in good agreement with well-established data from muonic, pionic, and kaonic helium.     

Entanglement in helium

Metallic Bi₂Te₃ crystalline sheets with the room-temperature resistivity of above 10 mΩ cm were prepared and their magnetoresistive transport was measured in a field of up to 9 T. The Shubnikov de Haas oscillations were identified from the secondly-derived magnetoresistance curves. While changing the angle between the field and normal axis of the sheets, we find that the oscillation periods present a cosine dependence on the angle. This indicates a two-dimensional transport due to the surface state. The work reveals a resolvable surface contribution to the overall conduction even in a metallic topological insulator.     

Kaonic helium atoms

Recent progress on the x-ray spectroscopy of kaonic helium atoms as well as on the precision laser spectroscopy of antiprotonic helium atoms are presented. Some historical background connecting these two exotic helium atoms is also discussed.     

Ultracold helium trimers

We summarize the results on binding energies and scattering observables for ⁴He-⁴He₂ and ³He-⁴He₂ collisions obtained with the Tang-Toennies-Yiu potential.     

Metastable States in Antiprotonic Helium Atoms: An Island of Stability in a Sea of Continuum

 In this contribution we consider a phenomenon of metastable states in antiprotonic helium atoms, precise spectroscopy of these states and a present-day study of the electromagnetic properties of antiprotons. Received October 16, 2001; accepted for publication November 13, 2001     

Trace detection of metastable helium molecules in superfluid helium by laser-induced fluorescence

We describe an approach to detecting ionizing radiation that combines the special properties of superfluid helium with the sensitivity of quantum optics techniques. Ionization in liquid helium results in the copious production of metastable He2 molecules, which can be detected by laser-induced fluorescence. Each molecule can be probed many times using a cycling transition, resulting in the detection of individual molecules with high signal to noise. This technique could be used to detect neutrinos, weakly interacting massive particles, and ultracold neutrons, and to image superfluid flow in liquid 4He.     

Metastable antiprotonic helium atomcules

The present status and future scope of the metastabe antiprotonic helium atomcules ¯pHe⁺ are described. Recently developed laser resonance spectroscopy has not only established the atomcule model but also triggered high-precision calculations of these atomcules.     

Kaonic hydrogen and helium

Coupled channels problem for kaonic hydrogen is solved using nonlocal potentials + Coulomb potential. It is applied for model and realistic problem for KH andKHe.Presented at the symposium Mesons and Light Nuclei, Bechyne, Czechoslovakia, May 27–June 1,1985.Supported in part by the DOE, Contract No. DE-ATO6-79ER10405.     

Ionic dipoles in helium

Attention has been focused on the apparent indications of the existence of ionic dipoles in solid helium. The presence of identical quasiparticles in cryogenic liquids with a positive scattering length of embedded electrons has been suggested. Possible manifestations have been discussed, which would allow the detection of the gas of dipolar structures in superfluid helium and the investigation of its behavior.     

Ions at helium interfaces

The boundaries between different phases of condensed helium provide an interesting testing ground for studying ions in a quantum matter matrix. Here we consider the simplest positive and negative ions in helium — snowballs and electron bubbles, respectively — being trapped at the liquid-liquid interface of phaseseparated³He–⁴He mixtures and at the liquid-solid interface of⁴He. A comparison of experimental results for the trapping with predictions of the snowball and the bubble models shows that the models are in qualitative accord with the observations, but disagree in detail. It is suggested to use such studies for refinements of the ion models. In addition multielectron bubbles (=mesoscopic ions) and electrons on helium films are briefly discussed.