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1.
Toshimitsu Yamazaki 《Hyperfine Interactions》2000,127(1-4):135-142
The metastable antiprotonic helium atom–molecule (in short, atomcule),
, which was discovered in 1991 as being the cause of the anomalous longevity of antiprotons with an overall lifetime of about
3 μs, now provides an exotic playground for laser spectroscopy, helped by the existence of numerous long lived states with
1–2 μs lifetimes. This three body system is characterized by a large angular momentum l ∼ 38 of
coupled with the electron in the 1s ground orbital, and looks like an exotic hydrogen isotope with many different “nuclear
states” as well as an exotic molecule with two centers (He2+ and
). So far, a number of laser resonance transitions have been identified. The present talk will cover the following topics:
(1) high precision spectroscopy in comparison with three body theories involving the relativistic effect and QED, and (2)
hyperfine structure of
;laser-microwave triple resonance.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
A. Werthmüller A. Adamczak R. Jacot‐Guillarmod F. Mulhauser L.A. Schaller L. Schellenberg H. Schneuwly Y.‐A. Thalmann S. Tresch 《Hyperfine Interactions》1998,116(1-4):1-16
The charge exchange reaction of negative muons from the
atom to oxygen has been measured in gaseous mixtures of H2 + O2. The measurements were performed at three different relative oxygen concentrations ranging from 0.2% to 0.8% and total pressures 3.5–15 bar. A mean transfer rate of
, describing the transfer from the ground state of thermalized
atoms to oxygen, was determined. In order to investigate the energy dependence of the transfer rate, Monte Carlo simulations of the
thermalization and the muon transfer were carried out. The comparison of measured and simulated time spectra yielded an epithermal transfer rate
=3.9
1011 s-1 in the energy interval 0.12–0.22 eV. The analysis with the model of Two components shows that all measured time spectra can be reproduced with the same set of parameters. 相似文献
3.
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
4.
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
5.
R. Orbach 《Hyperfine Interactions》1989,49(1-4):325-333
The excitation dynamics of site diluted magnets can be described at low energies (long length scales) by magnons, and above
a crossover frequency, ωc, (short length scales) by fractons. The density of fracton states is given by
, where
is the fracton dimensionality. Dilution gives rise to a characteristic length ξ∝(p−p
c)ν, wherep
c is the critical concentration for (magnetic) percolation. The crossover frequency ωc is proportional to ξ-1[1+(θ/2)], where θ is the rate at which the diffusion constant decays with distance for diffusion on an equivalent network. A fractal
dimensionD describes the density of magnetic sites on the infinite network, and
. For percolating networks,
for all dimensions ≥2. Neutron scattering structure factor measurements by Uemura and Birgeneau compare well with calculations
using fracton concepts.
Magnons are extended at low energies, while the fracton states are geometrically localized, with a wave function envelope
proportional to exp
. Here,
is the fracton length scale at frequency ω. The exponentd
ϕ lies between 1 andd
min, the chemical length index (of the order of 1.6 in three dimensions). The localization of the magnetic excitations causes
a spread in the NMR relaxation rates. A given nuclear moment will experience only a limited set of fracton excitations, resulting
in an overall non-exponential decay of the NMR relaxation signal. When strong cross-relaxation is present, the relaxation
will be exponential, but the temperature dependence will be strongly altered from the concentrated result. 相似文献
6.
G.Ya. Korenman 《Hyperfine Interactions》1999,119(1-4):227-233
Effect of medium density on shift and broadening of (
) spectral lines is considered in the framework of binary-collision approximation with an effective (
)–He potential including the long-range attraction and short-range repulsion. Quantum calculations of the scattering phase
shifts at reasonable values of the potential parameters allow to explain the main features of the observed density effect
on the shape of (
) spectral lines in low-temperature helium.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Yasunori Yamazaki 《Hyperfine Interactions》2001,138(1-4):141-152
The Antiproton Decelerator (AD) devoted primarily to atomic physics experiments has been stably operated since 2000. Until
now, three proposals have been approved, two of which are on the production and spectroscopy of antihydrogen, and the third
one is on atomic collisions and precision spectroscopy of antiprotonic atoms, ASACUSA collaboration. One of the unique features
of the ASACUSA collaboration is to develop intense slow and ultra slow antiproton beams of high quality, which will open a
new multidisciplinary field involving atomic physics, nuclear physics and elementary particle physics. The ultra slow antiprotons
will be prepared by combining the AD (down to 5.3 MeV), the RFQD (Radio Frequency Quadrupole Decelerator) (down to several
tens keV), and an electron cooling device which will be called “MUSASHI” (Monoenergetic Ultra Slow Antiproton Source for High-precision
Investigations) (down to several eV). MUSASHI produces the eV antiproton beam through an electron cooling of trapped antiprotons
and a radial compression followed by an extraction through a transport beam line. The transport beam line is specially designed
so that the pressure at the trap region can be maintained more than six orders of magnitude better than the collision region
and at the same time the transport efficiency is kept at almost 100%. The ultra slow antiproton beam allows for the first
time to study collision dynamics such as antiprotonic atom formation and ionization processes under single collision conditions,
and also to study spectroscopic nature of various metastable antiprotonic atoms such as
p,
He+,
He++, etc. Metastable
p are particularly interesting because they allow to make high precision spectroscopy of two body exotic atoms. Production
and spectroscopy of antiprotonic atoms consisting of unstable exotic nuclei will also be discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
The main properties of the interaction of ultra low‐energy antiprotons (E⩽10-6 a.u.) and antihydrogen with atomic hydrogen are established. Elastic and inelastic cross‐sections and Protonium formation
spectrum are calculated within quantum mechanical coupled channels approach. The results of calculations differ strongly from
predictions made by extrapolation of semiclassical models to the energy domain of interest. It is shown that the main feature
of the observables behaviour is determined by existence of a family of
H,
H near‐threshold metastable states.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
M.J. Prandolini W.D. Hutchison J. Leib D.H. Chaplin G.J. Bowden 《Hyperfine Interactions》1998,116(1-4):83-89
NMRON studies for the
54Mn transitions in antiferromagnetic MnBr2
4H2O, in the millikelvin regime, are presented and discussed. New values are given for (i) the sum of the effective molecular exchange and magnetic anisotropy fields acting on the Mn2+ ions,
=2.23(2) T, and (ii) the magnetic dipole hyperfine splitting, A=-201.99(1) MHz, electric quadrupole hyperfine splitting P=0.049(8) MHz and pseudoquadrupole splitting
=1.63(2) MHz for the 54Mn nuclei. 相似文献
10.
D. Verney F. Le Blanc L. Cabaret J. Crawford H.T. Duong J. Genevey G. Huber F. Ibrahim M. Krieg J.K.P. Lee D. Lunney J. Obert J. Oms J. Pinard J.C. Putaux B. Roussière J. Sauvage V. Sebastian 《Hyperfine Interactions》2000,127(1-4):79-82
Laser spectroscopy measurements have been performed on neutron deficient iridium isotopes. The hyperfine structure and isotope
shift of the optical Ir I transition 5d76s2
4F9/2 → 5d76s6p 6F11/2 at 351.5 nm have been studied for the 182–189Ir,
and 191,193Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the HFS measurements and the changes of the mean
square charge radii from the IS measurements. A large mean square charge radius change between 187Ir and 186Ir and between
and
has been observed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
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
12.
In view of current interest in the trapping of antihydrogen (
) atoms at low temperatures [1–3], we have carried out a full four-body variational calculation to determine s-wave elastic phase shifts for hydrogen antihydrogen scattering, using the Kohn Variational Principle. Terms outside the Born–Oppenheimer
approximation have been taken into account using the formalism of Kołos and Wolniewicz [4]. As far as we are aware, this is
the first time that these terms have been included in an H
scattering calculation. This is a continuation of earlier work on H–
interactions [5–7]. Preliminary results differ substantially from those calculated using the Born–Oppenheimer approximation
[8–10]. A method is outlined for reducing this discrepancy and taking the rearrangement channel into account.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Let
be the Haag--Kastler net generated by the
(2) chiral current algebra at level 1. We classify the SL(2,
)-covariant subsystems
by showing that they are all fixed points nets
H
for some subgroup H of the gauge automorphisms group SO(3) of
. Then, using the fact that the net
1 generated by the
(1) chiral current can be regarded as a subsystem of
, we classify the subsystems of
1. In this case, there are two distinct proper subsystems: the one generated by the energy-momentum tensor and the gauge invariant subsystem
. 相似文献
14.
15.
G. Filoti V.M. Meriacre E. Mateescu V. Kuncser K.I. Turta 《Hyperfine Interactions》1998,116(1-4):127-136
Six new
oxo trinuclear iron(III) complexes of the type [Fe3O(R–COO)6(H2O)3]
X, where X=
or Cl– and R=C5, C7, C8, C9 were synthesized and investigated by Infra Red, Mössbauer Spectroscopy and magnetic measurements. The data pointed to a high spin state (S=5/2) for iron and for antiferromagnetic interactions. The asymmetrical shape of the Mössbauer doublet and its temperature dependence was treated using the Blume relaxation model. The relaxation process is influenced by both X and R components. 相似文献
16.
The product of two real spectral triples
and
, the first of which is necessarily even, was defined by A.Connes as
given by
and, in the even-even case, by
. Generically it is assumed that the real structure
obeys the relations
,
,
, where the
-sign table depends on the dimension n modulo 8 of the spectral triple. If both spectral triples obey Connes'
>-sign table, it is seen that their product, defined in the straightforward way above, does not necessarily obey this
-sign table. In this Letter, we propose an alternative definition of the product real structure such that the
-sign table is also satisfied by the product. 相似文献
17.
F. Le Blanc 《Hyperfine Interactions》2000,127(1-4):71-78
The COMPLIS (COllaboration for spectroscopic Measurements using a Pulsed Laser Ion Source) experiment is carried out at the
ISOLDE Booster facility at CERN. The aim is to measure the hyperfine structure and the isotope shift of a series of radioactive
laser desorbed atoms by multiple step laser ionization. This technique is especially suitable for refractory elements not
directly available as beams from the isotope separator. By collecting a primary radioactive beam, it is possible to delay
the laser desorption as long as necessary to obtain the particular daughter of interest. Laser spectroscopy measurements have
been carried out on very neutron deficient gold, platinum and iridium isotopes. Magnetic moments μI, spectroscopic quadrupole moments
and changes of the nuclear mean square charge radius
along each isotopes series have been extracted. From some results, a detailed comparison with the predictions of the models
is presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Summary We present EELS cross-section data of surface phonons on Ag(001) along
. The inelastic intensity is due to the contribution of different modes which are not solved by the EEL spectrometer. However,
the shape of the inelastic intensity shows a strong dependence on impact energy for all wave vectors, which allows tuning
the EELS on the different modes. The dependence of the loss frequency on impact energy is at variance with the one reported
previously for
, leading to the conclusion that other modes contribute to the inelastic intensity besidesS
1 andL
1 which dominate at
.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
19.
Given a simple, simply laced, complex Lie algebra
corresponding to the Lie group G, let
be thesubalgebra generated by the positive roots. In this Letter we construct aBV algebra
whose underlying graded commutative algebra is given by the cohomology, with respect to
, of the algebra of regular functions on G with values in
. We conjecture that
describes the algebra of allphysical (i.e., BRST invariant) operators of the noncritical
string. The conjecture is verified in the two explicitly known cases,
2 (the Virasoro string) and
3 (the
string). 相似文献
20.
N. M. Agababyan V. V. Ammosov M. Atayan N. Grigoryan H. Gulkanyan A. A. Ivanilov Zh. Karamyan V. A. Korotkov 《Physics of Atomic Nuclei》2006,69(1):35-38
The influence of nuclear effects on the production of neutral strange particles (V
0) is investigated using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E
v
=3−30 GeV) at the Serpukhov accelerator. The mean multiplicity of V
0 particles in nuclear interactions,
, is found to exceed significantly that in “quasideuteron” interactions,
. The ratio of
is larger than that for π− mesons,
. It is shown that the multiplicity gain of V
0 particles can be explained by intranuclear interactions of produced pions.
The text was submitted by the authors in English. 相似文献