共查询到20条相似文献,搜索用时 187 毫秒
1.
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
2.
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
3.
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
4.
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
5.
B. I. Deutch 《Hyperfine Interactions》1992,73(1-2):175-191
The main suggested routes for atomic antihydrogen (
) formation will be reviewed in a pedestrian fashion. These are the following reactions:
, and (iii)
. The present status of the projects related to these reactions, as well as the projects' experimental scope, will also be
discussed or referred to. Some speculations will be made regarding the physics that can be yielded by an antihydrogen probe. 相似文献
6.
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
7.
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
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.
Stan Gudder 《Foundations of Physics》1999,29(6):877-897
This article begins with a review of the framework of fuzzy probability theory. The basic structure is given by the -effect algebra of effects (fuzzy events)
and the set of probability measures
on a measurable space
. An observable
is defined, where
is the value space of X. It is noted that there exists a one-to-one correspondence between states on
and elements of
and between observables
and -morphisms from
to
. Various combinations of observables are discussed. These include compositions, products, direct products, and mixtures. Fuzzy stochastic processes are introduced and an application to quantum dynamics is considered. Quantum effects are characterized from among a more general class of effects. An alternative definition of a statistical map
is given and it is shown that any statistical map has a unique extension to a statistical operator. Finally, various combinations of statistical maps are discussed and their relationships to the corresponding combinations of observables are derived. 相似文献
10.
11.
Carl M. Bender 《Czechoslovak Journal of Physics》2006,56(9):1047-1062
In this paper, two independent methods are used to show that the non-Hermitian
-symmetric wrong-sign quartic Hamiltonian H = (1/2m)p
2 − gx
4 is exactly equivalent to the conventional Hermitian Hamiltonian
. First, this equivalence is demonstrated by using elementary differential-equation techniques and second, it is demonstrated
by using functional-integration methods. As the linear term in the Hermitian Hamiltonian
is proportional to ℏ, this term is anomalous; that is, the linear term in the potential has no classical analog. The anomaly
is a consequence of the broken parity symmetry of the original non-Hermitian
-symmetric Hamiltonian. The anomaly term in
remains unchanged if an x
2 term is introduced into H. When such a quadratic term is present in H, this Hamiltonian possesses bound states. The corresponding bound states in
are a direct physical measure of the anomaly. If there were no anomaly term, there would be no bound states. 相似文献
12.
We show that there are canonical isomorphisms between Hochschild cohomology spaces
, where
is the algebra of smooth functions on a manifold M and
the space of skew multivector fields over M. This implies that continuous and differential deformation theories of
coincide. 相似文献
13.
Electric field gradient q and quadrupole interaction frequency
calculated at 256.7 K in the high pressure phase (orthorhombic) of
Ga metal are reported. The results are: q=+0.251 atomic units (au),
=5.479 MHz. These are compared with results from experiment and previous calculation available for the monoclinic phase of
Ga metal at normal pressure. The results from the previous calculation at 248 K are: q=-0.250 au and
=5.318 MHz. The result from experiment extrapolated to 256.7 K is:
=4.871 MHz. The sign reversal of the calculated q is attributed mainly to the change of point symmetry of the lattice from the orthorhombic to monoclinic. That the interaction frequency in high pressure phase is higher than experiment may be partly due to the increase of pressure and partly to the structural phase change. 相似文献
14.
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. 相似文献
15.
16.
Using the self-consistent pseudopotential method, we have calculated the binding energy of the image states for the (0001)
, and
surfaces of beryllium. It is shown for the (0001) face that there exists a pronounced resonance image state with n=1 and energy −0.95 eV at the point
of the surface Brillouin zone. In the
surface, which has a wide band gap in the vicinity of the vacuum level, the calculated image state with n=1 at the point
has energy −1.2 eV and is a surface state of gap type. For the
face in the vicinity of the point
band gaps are absent. However, the symmetry of the bulk states near the vacuum level enables the existence of a resonance
image state with n=1 and energy −0.6 eV.
Fiz. Tverd. Tela (St. Petersburg) 41, 935–940 (June 1999) 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.
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
19.
G.L. Borchert D. Anagnostopoulos M. Augsburger C. Castelli D. Chatellard J.P. Egger P. El Khoury M. Elble 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》2000,127(1-4):149-155
At the LEAR facility, CERN, antiprotonic Lα transitions in light elements have been investigated with a focussing crystal
spectrometer. The high resolution of the experiment allowed for the first time to resolve in
H the 23P0 state from the close lying states 23P2, 21P1, and 23P1. In
D the corresponding transitions were found to be more than an order of magnitude broader. To a large extent the results for
H support the meson exchange model.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
We discuss the behavior of magnetically trapped antihydrogen (
) at temperatures relevant for gravity and spectroscopy experiments (well below 1 K) and the possibilities of attaining these
temperatures. Two possible options are considered. In the discussion of the first one, i.e.
as admixture in cold H gas, we develop the quantum-mechanical theory of
-H (and also
-H) elastic and rearrangement collisions at ultra-low (sub-Kelvin) energies, when s-wave scattering in the incoming channel
dominates. The rate constant of rearrangement leading to
decay turns out to be large, which makes the possibilities for
collisional cooling in H gas and
-H coexistence rather limited. As we show, the most promising is the other option, i.e.
atoms in the collisionless regime. For this regime the possibility of one-dimensional adiabatic cooling of
is demonstrated by using the example of the Ioffe trap. This phenomenon, interesting from the fundamental point of view,
offers the opportunity to cool
below 1 mK. 相似文献