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1.
E. Widmann 《Hyperfine Interactions》2001,138(1-4):121-129
New results of the laser and microwave spectroscopy of antiprotonic helium “atomcules” obtained in the first year of operation
of the Antiproton Decelerator (AD) facility of CERN are presented. They include the discovery of three new resonant transitions
and the determination of the zero-density wavelength of six transitions with an accuracy of 130 ppb in the best case. Auger
rates of those states were also determined, and two of them were found to be several orders of magnitude larger than expected
from a simple estimate based on the multipolarity Δl, i.e., the jump in angular momentum required for the antiproton to reach the next lower-lying state of ionized
He++. Furthermore, a first signal of a two-laser microwave triple resonance to measure the hyperfine splitting in antiprotonic
helium was observed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
A beam of relativistic antihydrogen atoms — the bound state (
e+) — can be created by circulating the beam of an antiproton storage ring through an internal gas target. An antiproton which
passes through the Coulomb field of a nucleus will create e+e− pairs, and antihydrogen will form when a positron is created in a bound instead of continuum state about the antiproton.
The cross section for this process is roughly 3Z
2 pb for antiproton momenta about 6 GeV/c. A sample of 600 antihydrogen atoms in a low-emittance, neutral beam will be made in 1995 as an accidental byproduct of Fermilab
experiment E760. We describe a simple experiment, Fermilab Proposal P862, which can detect this beam, and outline how a sample
of a few-104 atoms can be used to measure the antihydrogen Lamb shift to 1 %.
Work supported in part by Department of Energy contract DE-AC03-76SF00515 (SLAC).
Work supported by Fondo Nacional de Investigación Científica y Tecnológica, Chile. 相似文献
3.
Andrew das Arulsamy 《Pramana》2010,74(4):615-631
We prove the existence of a Hamiltonian with ionization energy as part of the eigenvalue, which can be used to study strongly
correlated matter. This eigenvalue consists of total energy at zero temperature (E
0) and the ionization energy (ξ). We show that the existence of this total energy eigenvalue, E
0±ξ, does not violate the Coulombian atomic system. Since there is no equivalent known Hamilton operator that corresponds quantitatively
to ξ, we employ the screened Coulomb potential operator (Yukawa-type), which is a function of this ionization energy to analytically
calculate the screening parameter (σ) of a neutral helium atom in the ground state. In addition, we also show that the energy level splitting due to spin-orbit
coupling is inversely proportional to ξ eigenvalue, which is also important in the field of spintronics. 相似文献
4.
Cross-beam atomic collision experiment between ultra-low-energy antiprotons and a supersonic gas jet
H. A. Torii Y. Nagata H. Toyoda H. Imao N. Kuroda V. L. Varentsov Y. Yamazaki 《Hyperfine Interactions》2009,194(1-3):37-43
The antiproton is a unique projectile in the study of atomic collision physics. With an aim to produce an antiproton beam at atomic-physics energies for ‘pure’ collision experiments, we have so far developed techniques to decelerate, cool and confine antiprotons in vacuo. Our recent success in stable extraction of the beam has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom at an unprecedented low energy from 10 eV to 1 keV under the single-collision condition. We have prepared a powerful supersonic helium gas jet to be crossed with the antiproton beam. The reaction rate is of the order of 10???4, and rigorous identification of particles is required for reduction of huge background counts. The reaction events are recognized by an electron signal followed by antiproton annihilation with an appropriate interval in the time of flight. Our design and strategy of the experiment are presented. 相似文献
5.
P. D. Grigor’ev 《JETP Letters》1997,66(9):630-636
The energies and widths of the levels of an electron on impurity centers on the surface of liquid helium are calculated with
allowance for the deformation of the surface. The level shift associated with the deformation effects is small and decreases
very slowly with increasing level number. However, even a small shift of the energy levels relative to one another affects
ripplon scattering, which makes the main contribution to the level width at low temperatures. It is predicted theoretically
that this width depends very strongly on the external parameters and on the level number and that a maximum obtains at a clamping
field E
⊥=51500 V/cm. The width of the levels of an electron in a bound state is found to be less than for free electrons. This makes
it possible to perform a beautiful spectroscopic experiment.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 9, 599–604 (10 November 1997) 相似文献
6.
We precisely calculated the energy levels and the Auger decay rates of the antiprotonic helium atoms with the coupled rearrangement
channel method and the complex-coordinate-rotation method. Calculated transition frequencies were in excellent agreement with
observed values. This agreement gives best limit of the antiproton mass with 5×10−8 uncertainty.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
E. H. Baksht M. I. Lomaev D. V. Rybka D. A. Sorokin V. F. Tarasenko 《Technical Physics》2008,53(12):1560-1564
The parameters of an electron beam generated in helium in the pressure range p = 10−4−12 atm are studied. Nanosecond high-voltage pulses are applied to a gap between a tubular cathode and planar anode, which
is made of 45-μm-thick AlBe foil. Behind the anode, an electron beam is detected at a helium pressure of 12 atm. The pressure
dependence of the beam current amplitude shows three peaks at p ≈ 0.01, ≈ 0.07, and ≈ 3 atm. The beam-induced glow of a luminescent film placed behind the foil and the discharge glow at
different helium pressures in the gas-filled diode are photographed. 相似文献
8.
A. A. Krutov A. P. Martynenko 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,62(2):163-175
On the basis of the perturbation theory in the fine structure constant α and the ratio of the electron to muon masses we calculate one-loop vacuum polarisation and electron vertex corrections and
the nuclear structure corrections to the hyperfine splitting of the ground state of the muonic helium atom (μ e
3
2He). We obtain total results for the ground state hyperfine splitting Δ
ν
hfs
= 4166.648 MHz which improves the previous calculation of Lakdawala and Mohr due to new corrections of orders α
5 and α
6. The remaining differences between our theoretical result and experimental value of the hyperfine splitting lie in the range
of theoretical and experimental errors and require the subsequent investigation of higher order corrections. 相似文献
9.
Spectroscopy of antiprotonic helium atoms and its contribution to the fundamental physical constants
Ryugo S. Hayano 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(1):1-10
Antiprotonic helium atom, a metastable neutral system consisting of an antiproton, an electron and a helium nucleus, was serendipitously discovered, and has been studied at CERN’s antiproton decelerator facility. Its transition frequencies have recently been measured to nine digits of precision by laser spectroscopy. By comparing these experimental results with three-body QED calculations, the antiproton-to-electron massratio was determined as 1836.152674(5). This result contributed to the CODATA recommended values of the fundamental physical constants. 相似文献
10.
Cai Lingcang Chen Qifeng Gu Yunjun Zhang Ying Zhou Xianming Jing Fuqian 《中国科学G辑(英文版)》2005,48(2):695-705
Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6, 1.2,
and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer. It was found that
the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was
in good agreement with the experimental data. The curve of the calculated shock wave velocity with the particle velocity of
gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K, i.e., theD ≈u relation,D=C
0+λu (u<10 km/s, λ=1.32) in a low pressure region, is approximately parallel with the fittedD ≈u (λ=1.36) of liquid helium from the experimental data of Nellis et al. Our calculations show that the Hugoniot parameter λ
is independent of the initial density p{in0}. TheD≈u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates
to about 18000 K and the ionization degree of the shocked gas helium reaches 10−3. 相似文献
11.
Antiprotonic helium is a metastable three-body neutral atom consisting of an antiproton, a helium nucleus and an electron, which we serendipitously discovered some 20 years ago. The antiproton, which normally annihilates within a few picoseconds when injected into matter, can be “stored” in this system for up to several microseconds, and laser spectroscopy is possible within this time window. From the laser transition frequency, the antiproton-to-electron mass ratio can be deduced to high precision. Recent progress at CERN’s antiproton decelerator (AD) will be discussed. 相似文献
12.
CAI Lingcang CHEN Qifeng GU Yunjun ZHANG Ying ZHOU Xianming & JING Fuqian Laboratory for Shock Wave Detonation Physics Research Institute of Fluid Physics Mianyang China 《中国科学G辑(英文版)》2005,48(6):695-705
Helium, hydrogen, and their isotopes are the simplest monoatomic and diatomic molecules. It is relatively easy to describe their properties using the basic principles of quantum mechanics. In condensed matter physics, hydrogen and helium serve as the models for the condensed matter properties at extreme conditions so that both experi- mental and theoretical physicists pay much attention to the study of their properties[1], especially the insulator-metal transition of hydrogen[2]. The aim to st… 相似文献
13.
The catalogue of negative ions in superfluid helium has been extended using the example of Ar−, Kr−, and Xe−. Such objects cannot exist in vacuum, since the polarization attraction of an electron to the inert A atom is insufficient
for the formation of the bound state A−. However, these objects exist in helium as stable or metastable with a very long lifetime. The effect is due to the electron
localization in liquid helium. If a mixture of excited A* atoms and electrons is prepared in the gas phase above liquid helium,
the reaction A* + e = A*− becomes possible for all atoms of the periodic table. Such charges can be immersed into liquid helium by the electric field.
In this case, the radiative decay A*− = A + e allowed in vacuum can be forbidden in liquid. This leads to the formation of the new unique objects A−, which can exist in liquid helium but are absent in nature. The size of such charged formations has been determined and is
close the radius of a usual electron bubble in helium. 相似文献
14.
The Born-Oppenheimer approximation is used to discuss the high rotational and vibrational state of the (He p−)e− system in the electronic 1sσ and 2pσ states. Very high angular momentum states, in which the antiproton is well outside the
electron orbit, have a Rydberg-like character. states in which the antiproton is within the 1sσ electron orbit have enhanced
radiative lifetimes due to the polarization of the 1sσ state by the antiproton. This effect may account for the long-lived
component observed in antiproton destruction in He. Preliminary results on the effect of coupling to the 2pσ well, in which
the polarization effects enhance the decay rate, are also presented. Some consequences for the suggestion that metastable
antiprotonic He atoms may be used to promote antihydrogen formation are discussed. 相似文献
15.
The rate constant for spin exchange in a system consisting of a metastable helium atom and an alkali-metal atom is determined.
An experiment on optical orientation of atoms established that the rate constant for spin exchange in a collision of a metastable
23
S
1 helium atom with a cesium atom in the 62
S
1/2 ground state equals (2.8±0.8)×10−9 cm3 s−1. The rate constant for chemoionization of cesium atoms by metastable helium atoms was determined at the same time to be (1.0±0.3)×109 cm3s−1.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 145–148 (10 August 1997) 相似文献
16.
Recurrence spectra of He atoms in strong external fields 总被引:1,自引:0,他引:1
LIN Shenglu LI Hongyun WANG Dehua ZHAO Wenli & GAO Feng . Department of Physics Shandong Normal University Jinan China . Department of Mathematics Physics Shandong Institute of Architecture Engineering Jinan China 《中国科学G辑(英文版)》2004,47(4):477-484
1 Introduction The photo-absorption phenomenon of high Rydberg atoms in strong external fields has attracted much attention in recent years. The semiclassical closed-orbit theory[1,2] developed by Du and Delos has been extensively used to explain this phenomenon. This theory has successfully calculated and interpreted the photo-absorption spectra of H- in various external fields[3,4] and has been applied to describe the photo-excitation, wave packet dynamics of some atoms and molecules such… 相似文献
17.
J. N. Kavanagh F. J. Currell D. J. Timson M. H. Holzscheiter N. Bassler R. Herrmann K. M. Prise G. Schettino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(1):209-214
Radiotherapy employs ionizing radiation to induce lethal DNA lesions in
cancer cells while minimizing damage to healthy tissues. Due to their
pattern of energy deposition, better therapeutic outcomes can, in theory, be
achieved with ions compared to photons. Antiprotons have been proposed to
offer a further enhancement due to their annihilation at the end of the
path. The work presented here aimed to establish and validate an
experimental procedure for the quantification of plasmid and genomic DNA
damage resulting from antiproton exposure. Immunocytochemistry was used to
assess DNA damage in directly and indirectly exposed human fibroblasts
irradiated in both plateau and Bragg peak regions of a 126 MeV antiproton
beam at CERN. Cells were stained post irradiation with an anti-γ-H2AX antibody. Quantification of the
γ-H2AX foci-dose relationship is consistent with a linear increase in the Bragg peak region. A qualitative analysis of the
foci
detected in the Bragg peak and plateau
region indicates significant differences highlighting the different severity
of DNA lesions produced along the particle path. Irradiation of desalted
plasmid DNA with 5 Gy antiprotons at the Bragg peak resulted in a significant
portion of linear plasmid in the resultant solution. 相似文献
18.
Widmann E Eades J Ishikawa T Sakaguchi J Tasaki T Yamaguchi H Hayano RS Hori M Torii HA Juhász B Horváth D Yamazaki T 《Physical review letters》2002,89(24):243402
Using a newly developed laser-microwave-laser resonance method, we observed a pair of microwave transitions between hyperfine levels of the (n,L)=(37,35) state of antiprotonic helium. This experiment confirms the quadruplet hyperfine structure arising from the interaction of the antiproton orbital angular momentum, the electron spin and the antiproton spin as predicted by Bakalov and Korobov. The measured frequencies of nu(+)(HF)=12.895 96+/-0.000 34 GHz and nu(-)(HF)=12.924 67+/-0.000 29 GHz agree with recent theoretical calculations on a level of 6x10(-5). 相似文献
19.
A. Wolf G. Uhlenberg U. Schramm T. Schüßler A.E. Livingston G. Gwinner G. Saathoff D. Schwalm 《Hyperfine Interactions》2000,127(1-4):203-210
Spectroscopic results obtained on multiply charged few electron ions by using laser stimulated two-step recombination in ion
storage rings are presented in an overview. Line splittings in transitions between Rydberg levels were observed for helium
like and beryllium like ions. Emphasis is given to results on the beryllium like system N3+ where information about the splitting between high angular momentum levels (l⩾4) was obtained for the Rydberg levels n=13 and 8 with experimental errors of about ±0.02 meV.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
We present the measurement of directed flow (v
1) for the identified particles, namely, Λ, $
\bar \Lambda
$
\bar \Lambda
and K
s
0, as a function of rapidity and centrality in Au+Au collisions at $
\sqrt {s_{NN} }
$
\sqrt {s_{NN} }
= 200 GeV and 62.4 GeV. The measurement is based on the run IV data obtained by the STAR experiment at RHIC. In order to
enhance event plane resolution, we use tracks reconstructed from the Forward Time Projection Chambers (FTPCs), together with
the sideward deflection of spectator neutrons measured by the STAR’s Shower Maximum Detector at Zero Degree Calorimeters (ZDC-SMDs).
We find that for 200 GeV, proton and antiproton v
1 is less than 1%, the K
s
0
Λ, $
\bar \Lambda
$
\bar \Lambda
v
1 is less than 2%; for 62 GeV, proton v
1 is less than 1% and antiproton is less than 2%, v
1 for K
s
0, Λ, $
\bar \Lambda
$
\bar \Lambda
is less than 2% in Au+Au collisions at 200 GeV. 相似文献