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1.
V.I. Korobov 《Hyperfine Interactions》1999,119(1-4):185-193
We discuss the latest theoretical achievements in calculations of energy transitions in the antiprotonic helium He+
p-0304; atoms. New variational calculations of the nonrelativistic energies with precision of ∼10-10 a.u. and relativistic and QED corrections to the energy levels of mα
5 order are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Leonid I. Men'shikov 《Hyperfine Interactions》1999,119(1-4):245-250
A new interpretation of the nature of the metastable states of antiprotons in helium is proposed. The first step is the formation
of an ion (
), which shall be called “ioncule”. After its decay a neutral “atomcule” (
) is formed which was observed in the experiments on metastable antiprotonic helium. This model explains the experiments in
a natural way, in particular the quenching by atomic and molecular admixtures and the pressure dependence of quenching in
pure helium. At high helium densities the ioncule creates a vacuum bubble in helium. It is shown that the annihilation of
slowed-down
can be suppressed at helium pressures of ∼ 10 000 bar.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
Auger decay rates of the metastable antiprotonic helium 3,4He
e are calculated. The variational method and solution of coupled differential equations are combined to determine the initial
metastable state wave function. Besides metastable states, the calculation reveals specific short-lived states of the antiprotonic
helium with an essentially different structure of the wave function. An effect of mixture of the wave functions is taken into
account to calculate the decay rate for a few metastable states, which are close in energy to the short-lived ones.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Hiroyuki A. Torii 《Hyperfine Interactions》1999,119(1-4):213-219
We have performed laser spectroscpy of metastable antiprotonic helium atoms (or “atomcules”) (
He+) and have observed a density dependence of the resonance vacuum wavelengths for the known transitions (n,l)=(39,35)→(38,34) and (37,34)→(36,33). They showed linear red-shifts of 0.61±0.01 GHz and 0.22±0.02 GHz per 1 g℞, respectively. With the shift parameters above, the transition vacuum wavelengths were extrapolated to zero-density limits,
yielding λ0 = 597.2570± 0.0003 nm and λ0 = 470.7220±0.0006 nm, respectively. These values were compared with the result of recent theoretical calculations on the
energy of the Coulombic three-body system, including relativistic corrections and the Lamb shift. The agreements between our
experimental values and the calculations have become as good as 2×10-6. This sets a severe constraint on the antiproton charge (
) and mass (
) with |Q
p -
|/e < 5 × 10-7 and |M
p
-
|/M
p
< 5 × 10-7, under a more precisely known constraint on the charge-to-mass ratio. Thus we have opened a new possibility of measuring
fundamental constants of the antiproton.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Muonic X-ray spectra from Ar and H2 + Ar have been measured with a high-pressure gas target. Strong differences between the observed intensities of corresponding lines were found for the two cases. The results are compared with cascade calculations. The ratio between Coulomb capture in Ar and in Ne for an Ar-Ne mixture (atomic ratio 1:1) was determined to be 1.11±0.14. 相似文献
6.
G.L. Borchert D. Anagnostopoulos M. Augsburger D. Belmiloud C. Castelli D. Chatellard M. Daum J.P. Egger P. El-Khoury M. Elble R. Frosch H. Gorke D. Gotta P. Hauser P. Indelicato K. Kirch S. Lenz N. Nelms K. Rashid O.W.B. Schult Th. Siems L.M. Simons 《Hyperfine Interactions》1998,114(1-4):157-164
Some time after its formation an exotic atom may be considered a hydrogen-like system consisting of a nucleus and an exotic
particle in a bound state. In this situation it is an ideal tool to study cascade properties, while for the innermost orbits
it can be used to probe the interaction with the nucleus. From an extended series of experiments using high resolution X-ray
spectroscopy for both aspects typical examples are reported and preliminary results are given: 1. To determine the complex
scattering length in
H the
hyperfine transitions have been measured. 2. To determine the pion mass the 5
4 transitions in
N have been studied. In all cases a major contribution to the uncertainty originates from the calibration. Therefore a new
method is proposed that will establish a universal set of high precision calibration lines for pionic, muonic and electronic
systems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
The authors have measured the transmission of a positron beam through helium, neon and argon gases from 4 eV up to the positronium formation thresholds. A variable longitudinal magnetic field affects the transmission and allows some degree of phase shift separation, analogously to the performance of an angular distribution experiment. The results for neon and argon are presented. 相似文献
8.
The energy levels of the metastable states of Coulombic exotic three-body systems were calculated with the non-adiabatic coupled
rearrangement channel method. The resonant boundary condition of the metastable levels is taken into account. Relativistic
and QED corrections on the energies were made. Excellent agreement between corrected wavelengths and experimental data was
achieved. This agreement gave the best limit of the antiproton mass with 10-7 uncertainty.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
We investigate the state-specified capture process of antiprotons by helium. Freezing one of the two electrons, we reduce this four-body rearrangement problem into a three-body problem. The capture cross sections are calculated by solving the Chew-Goldberger-type integral equation. Differing from the capture of antiprotons by hydrogen atoms, the bumpy structures are revealed in the total angular momentum dependent capture cross sections. Further analysis shows that the bumps arise from the partial channel closing due to the removal of the energy degeneracy in the antiprotonic helium. 相似文献
10.
S. A. Elkilany 《Il Nuovo Cimento D》1998,20(2):147-154
Summary Partial and total cross-sections of electrons scattering by helium and neon atoms are calculated at eleven values of incident
energy ranging from 0.1 a.u. to 1.1 a.u. The calculations are carried out via model potential (describing the electron target
interaction). The iterative Green’s function partial-wave expansion technique was used. The comparison between our results
and those obtained by other authors show significant agreement and supports our simple model scattering process. 相似文献
11.
12.
G.H. Copley 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(7):553-558
Self broadening (van der Waals and resonance) and shift of Ne emission lines and van der Waals broadening and shift of He emission lines have been measured using a high pressure (0.5–3.0 atom), low current discharge. These results are compared with previous measurements in Ar and He to obtain a complete comparison of self broadening and shift of He, Ne and Ar emission lines. Oscillator strengths for the resonance transitions are obtained from the resonance broadening coefficients. The trend of the van der Waals broadening coefficients for the three noble gases is correctly predicted by a theory due to HINDMARSHet al.(4) in which a Lennard-Jones potential is used in the impact theory formalism. The measured line shifts cannot be accounted for by this theory and reflect the need for more accurate quantum mechanical calculations. 相似文献
13.
An ab initio investigation of the density dependence of the electric-field-gradient induced birefringence (EFGB) for the noble gases helium, neon and argon is presented. To determine the second coefficient in the virial expansion of the molecular EFGB constant mQ, the effect of two-body interactions has been studied by computing the internuclear dependence of the molecular quadrupole moment and of the dipole-dipole-quadrupole and dipole-magnetic dipole-dipole hyperpolarizabilities of the van der Waals dimers. A full-configuration-interaction approach as well as the coupled cluster singles and doubles and the coupled cluster singles and doubles plus perturbative triples approximations have been adopted, and extended basis sets including midbond functions have been employed. A semi-classical integration yields the virial coefficients. The effect of density for standard experimental conditions is found to be of the order of a few tens of parts per million for helium and neon, and of the order of a few parts per thousands for argon at low temperatures, and thus not detectable with present apparatus. 相似文献
14.
15.
Y. -A. Thalmann R. Jacot-Guillarmod F. Mulhauser C. Piller L. A. Schaller L. Schellenberg H. Schneuwly S. Tresch A. Werthmüller 《Zeitschrift für Physik A Hadrons and Nuclei》1997,359(2):219-224
The yields of muonic x rays of the Lyman series of nitrogen, neon and argon have been analysed to determine capture ratios A(Z1,Z2) in about thirty gaseous mixtures under different experimental conditions. In addition, capture ratios A(Z,H) have been determined in hydrogen mixtures by taking into account transfer processes from muonic hydrogen to elements Z. The influence of the spectral flux density of the muons on capture ratios has been analysed. Our per-atom ratios form a coherent set and confirm the value A(Ar,Ne) = 1. 262(10). 相似文献
16.
T. C. Griffith G. R. Heyland K. S. Lines T. R. Twomey 《Applied Physics A: Materials Science & Processing》1979,19(4):431-437
A slow positron beam time of flight system in which scattering is localised to a region of the flight path close to the slow
positron source is described. Total cross-sections measured in helium, neon, and argon at intermediate energies are presented.
The results for helium and neon are in agreement with the recent results of Brenton et al. While significant disagreement
still exists in the argon data. The helium and neon data are in agreement with the sum rule predictions of Bransden et al. 相似文献
17.
18.
The QCMC scheme created earlier for cascade calculations in heavy hadronic atoms of hydrogen isotopes has been modified and
applied to the study of cascade processes in the μp muonic hydrogen atoms. The distribution of μp atoms over kinetic energies has been obtained and the yields of K-series X-rays per one stopped muon have been calculated.
Comparison with experimental data indicated directly that for muonic and pionic atoms new types of non-radiative transitions
are essential, while they are negligible for heavy (kaonic, antiprotonic, etc.) atoms. These processes have been considered
and their probabilities have been estimated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Measurements are reported of ambipolar diffusion coefficients as determined from ion density loss rates, and of electron temperatures determined using the single Langmuir probe technique, in afterglow plasmas of spectroscopically pure neon, argon and krypton. In each gas there was a critical pressure,p 0 c , above which the product of the ambipolar diffusion coefficient,D a , and the reduced gas pressure,p 0, was pressure independent and above which the electron temperature was found to cool asymptotically to the gas temperature. For pressures belowp 0 c ,D a p 0 decreased with decreasing pressure, and the electron temperature cooled asymptotically to a steady equilibrium value,T eq, below the gas temperature, this equilibrium value itself decreasing with decreasing gas pressure. These results clearly show that diffusion cooling of electrons was taking place at these low gas pressures. A detailed study of the krypton afterglow showed that the values ofD a p 0 andT eq for a given gas pressure were related in a manner predicted by simple diffusion theory. During the course of these measurements values for the zero field mobilities of Ne+, Ar+ and Kr+ ions in their parent gases were obtained and are also reported. 相似文献
20.
The antiproton-nucleus annihilation in two possible experimental situations (low energy in-flight annihilation and annihilation in a trap) is investigated taking into account the Coulomb interaction. For these two cases, the formulas giving the relation between the antiproton-nucleus scattering lengtha cs and observables (annihilation cross section and antiprotons time-of-life in a trap) are obtained. These relations are proposed to determinea cs. 相似文献