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1.
The He-Ar-Cu+ IR laser operates in a hollow-cathode discharge, typically in a mixture of helium with a few-% Ar. The population inversion
of the Cu+ ion levels, responsible for laser action, is attributed to asymmetric charge transfer between He+ ions and sputtered Cu atoms. The Ar gas is added to promote sputtering of the Cu cathode. In this paper, a hybrid modeling
network consisting of several different models for the various plasma species present in a He-Ar-Cu hollow-cathode discharge
is applied to investigate the effect of Ar concentration in the gas mixture on the discharge behavior, and to find the optimum
He/Ar gas ratio for laser operation. It is found that the densities of electrons, Ar+ ions, Arm
* metastable atoms, sputtered Cu atoms and Cu+ ions increase upon the addition of more Ar gas, whereas the densities of He+ ions, He2
+ ions and Hem
* metastable atoms drop considerably. The product of the calculated Cu atom and He+ ion densities, which determines the production rate of the upper laser levels, and hence probably also the laser output power,
is found to reach a maximum around 1–5 % Ar addition. This calculation result is compared to experimental measurements, and
reasonable agreement has been reached.
Received: 14 October 2002 /
Revised version: 28 November 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +32-3/820-23-76, E-mail: annemie.bogaerts@ua.ac.be 相似文献
2.
3.
R. H. Scheicher A. N. U. Roy T. P. Das K. Ishida T. Matsuzaki S. N. Nakamura N. Kawamura K. Nagamine 《Hyperfine Interactions》2001,138(1-4):387-395
The study of trapping of He+ ion in solid hydrogen is important both as a problem in solid state physics and also as an applied physics problem in the
field of muon catalyzed fusion (μCF). In μCF, He+ ion acts as a trap for μ−, interrupting the chain reaction aspect of the catalytic role of μ− in producing fusion of deuteron and triton and of triton and triton in solid hydrogen composed of 2H–3H and 3H–3H molecules, respectively. Using the Hartree–Fock procedure, combined with procedures for including many-body effects, as
well as relaxation effects associated with the He+–H2 distances and the adjustment of the H–H separation, we have investigated the trapping of He+ in gaseous and solid state environments. For the former, the environment of He+ is simulated by a single hydrogen molecule and for the solid by clusters appropriately chosen to represent the hexagonal
close-packed structure. Our results for the gaseous state indicate that the trapping is rather strong with a binding energy
of 8.5 eV, with almost equal binding energy in the linear and triangular configurations with respect to the H–H direction.
For the solid, both the likely sites for He+ trapping, namely the tetrahedral and octahedral interstitial sites, are also found to provide deep traps (8.6 eV) of almost
equal strength, independent of the orientations of the neighboring molecules, showing that the trapping is not influenced
by the orientational disorder in the surrounding hydrogen molecules. Further, the influence of next nearest neighbor hydrogen
molecules is found to enhance the trapping energy for He+ substantially, by 0.6 eV, with the incorporation of the third nearest neighbors having a much smaller added effect, demonstrating
the convergence of our results with respect to the size of the cluster chosen to simulate the solid. The substantial influence
on the He+ trapping energy found for the neighbors beyond the nearest ones provides an explanation of the greater accumulation of helium
in the solid state of hydrogen in μCF experiments as compared to the liquid. Suggestions are made regarding the possible reasons
for the almost negligible accumulation of helium in the liquid state.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Elastic and inelastic scattering cross-sections in the 3,4Hedμ systems near the dμ threshold are calculated. The isotopic effect and strong energy dependence in 4Hedμ are found. The reason for these peculiarities is the near-threshold pole of the 4Hedμ scattering amplitude.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
A. Méry G. Ban J. Blieck D. Durand F. Duval X. Fléchard M. Herbane M. Labalme Y. Lemière E. Liénard F. Mauger O. Naviliat-Cuncic D. Rodríguez J. C. Thomas 《The European physical journal. Special topics》2007,150(1):385-388
The existence of exotic couplings in the weak interaction can be
tested by a precise measurement of the β-ν angular correlation parameter a in nuclear beta decay. In the case of 6He, the
ratio of tensor and axial-vector couplings can be determined. The goal of the LPC Trap experiment is to improve the limits
on the
existence of
tensor currents. The LPCTrap setup is installed on the low energy beam
line LIRAT of the SPIRAL/GANIL facility. The 6He+ ions are confined in a novel transparent Paul trap
allowing the detection in coincidence of both the β-particle and the recoil ion. The detection setup enables to detect the
position and energy of these two particles. The a parameter can then be extracted from the time of flight spectrum of the
recoil ions. The first 6He+ decay events were observed in May 2005 during a commissioning run. Over 105
coincidence events have been recorded during a second run in July 2006. 相似文献
6.
I.?Man?ev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(2):213-218
The total cross sections for charge transfer in Li2+-H and He+-He+ collisions have been calculated, using the four body first Born approximation with correct boundary conditions (CB1-4B) and
four body continuum distorted wave method (CDW-4B) in the energy range 10–5000 keV/amu. The role of dynamic electron correlations
is examined as a function of the impact energy. The present results call for additional experimental data at higher impact
energies than presently available. 相似文献
7.
Y. K. Ho 《Hyperfine Interactions》1992,73(1-2):109-130
Theoretical studies of atomic resonances involving positrons will be discussed in this talk. Investigations on resonances
in positron-hydrogen scattering below various hydrogen and positronium thresholds are reviewed, as well as resonances in positronalkali
and e+-He+ scattering. Resonance phenomena in other atomic systems involving positrons will also be discussed. These systems include
positronium ions Ps−, positronium molecules Ps2, and positronium hydride PsH. 相似文献
8.
R. H. Scheicher T. P. Das K. Ishida T. Matsuzaki S. N. Nakamura N. Kawamura K. Nagamine 《Hyperfine Interactions》2001,138(1-4):431-434
We are involved in a program aimed at a first-principles examination of the possibility of helium bubble formation in solid
hydrogen. Our procedure is based on an extension of the Hartree–Fock cluster approach that we have been using for study of
individual He+ ions in solid hydrogen. The preliminary results of our cluster investigations of a particular configuration of two He+ ions in neighboring tetrahedral interstitial positions are presented here. It has been found that the hydrogen molecules
common to the two He+ ions lead to a substantial attractive force between the ions that almost overcomes their inherent repulsion, leading to a
binding energy for this configuration only slightly less than the binding energy for two well separated trapped He+ ions. The analysis of our results have suggested future investigations of different pairs of trapping sites which appear
to be more favorable for providing higher binding energies for the He+ pairs.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
R. H. Scheicher T. P. Das K. Ishida T. Matsuzaki S. N. Nakamura N. Kawamura K. Nagamine 《Hyperfine Interactions》2001,138(1-4):427-430
We are currently investigating the influence of vibrational effects on the strength of trapping of He+ in solid hydrogen. Such effects can lead to an isotope dependence of the trapping energy associated with the hydrogen molecules
and He+ ion. At the present time, our focus is on the isotope effect for 3He+ and 4He+, which we are studying through the vibrational motions of the trapped He+ ions in the potential they experience as they move about their equilibrium positions. The potential governing the vibrations
has been obtained from Hartree–Fock cluster calculations of the total energy of the cluster composed of the He+ ion and up to the third nearest neighbor hydrogen molecules as a function of the displacement of the He+ ion from its trapped position. The energy eigenvalues for the ground vibrational states of 3He+ and 4He+ in this potential come out as 1.29 and 0.96 meV, respectively, leading to corresponding reductions by these amounts in the
binding energy of 8.6 eV for both ions without vibrational effects. The difference of these reductions can be considered as
an isotope shift, its value for this case being 0.33 meV. From the analysis for these results, it is suggested that isotope
shift effects for deuteron and triton in solid D–T would have the same order of magnitude. A procedure for more accurate investigations
of the isotope shifts is discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
V. S. Kulhar 《Pramana》2004,63(3):543-551
The muonium/muonic hydrogen atom formation in μ±−H collisions is investigated, using a two-state approximation in a time dependent formalism. It is found that muonium cross-section
results are similar to the cross-section results obtained for positronium formation in e+-H collision. Muonic hydrogen atom formation cross-sections in μ--H collision are found to be significant in a narrow range of energy (5 eV–25 eV). 相似文献
11.
Using the pseudopotential method, theoretical investigation has been made on the firstorder Korteweg-deVries ion-acoustic
solitons in a multicomponent plasma consisting of warm positive ions, negative ions and isothermal electrons. The effects
of electron-inertia and drift motion of the ions on the amplitudes and widths of the solitons have been studied in a plasma
having (H+, Cl−), (H+, O−), (He+, H−) and (He+, O−) ions. Ion-acoustic double-layers have also been investigated for such plasmas. It has been found that drift velocity and
electron-inertia have significant contribution on the formation of double-layers in multicomponent plasma 相似文献
12.
M. Janek T. Saito V. P. Ladygin T. Uesaka M. Hatano A. Yu. Isupov H. Kato N. B. Ladygina Y. Maeda A. I. Malakhov J. Nishikawa T. Ohnishi H. Okamura S. G. Reznikov H. Sakai S. Sakoda N. Sakamoto Y. Satou K. Sekiguchi K. Suda A. Tamii N. Uchigashima T. A. Vasiliev K. Yako 《The European Physical Journal A - Hadrons and Nuclei》2007,33(1):39-46
The data on the tensor Ayy, Axx, Axz and vector Ay analyzing powers in the dd → ^3Hen obtained at T
d = 270 MeV in the angular range 0° - 110° in the c.m. are presented. The observed negative sign of the tensor analyzing powers Ayy, Axx and Axz at small angles clearly demonstrate the sensitivity to the ratio of the D - and S -wave component of the 3He wave function. However, the one-nucleon exchange calculations by using the standard 3He wave functions have failed to reproduce the strong variation of the tensor analyzing powers as a function of the angle
in the c.m. 相似文献
13.
A. N. Perumal D. N. Tripathi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):169-176
Classical Trajectory Monte-Carlo (CTMC) method has been used to investigate state selective electron capture by He2+ ions colliding with Li(2s) and Li(2p) in as well as alignments in the energy range 1-15 keV/amu. He+(4l) electron capture, line emission [He II(n = 4 3)] cross-sections and alignment parameters have been calculated and analyzed in the light of the available results. The
undulatory structure of the capture and emission cross-sections have been explained qualitatively in terms of a quasi-molecular
ion formation. Projectile impact energy and spatial overlap play crucial role in determining the alignment effects.
Received 3 July 1998 and Received in final form 3 June 1999 相似文献
14.
It is shown experimentally that a change in the mass of bombarding ions from 40Ar+ to 4He+ has a strong effect on the spatial distributions of the components sputtered from the alloy NiMoRe. A mechanism of sputtering
by backscattered ions is proposed to describe the observed preferential ejection of the light component in the direction normal
to the surface of the sample under bombardment by 4He+ ions.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 507–510 (10 April 1996) 相似文献
15.
F.A. Deeney 《Physics letters. A》2019,383(7):589-592
Following on our earlier work in this area, here we examine in some detail the physical mechanism involved in the Bose–Einstein condensation process. In particular we emphasise the significance of the zero value of the chemical potential at and below the critical temperature. The molar zero-point energy (ZPE) for an ideal gas of He4 atoms in our new analysis is estimated and found to be very close to that calculated for an ideal Fermi gas of He3 atoms under the same conditions. This gives numerical support to our theory. We also show how the theory is consistent with the presence of a density maximum in liquid He4. 相似文献
16.
Pritikana Khan P. S. Mazumder A. S. Ghosh 《Zeitschrift für Physik A Hadrons and Nuclei》1984,318(1):19-23
Scattering of positrons by hydrogen-like-ions (He+, Li2+, Be3+ and B4+) has been studied using two variants of the polarized orbital method. The positronium formation channel has not been included in the calculations,s-wave phase shifts obtained using the two variants differ appreciably from each other. Moreover, the polarized orbitals-wave phase shifts fore +-B4+ scattering differ from the corresponding variational results qualitatively in the low energy region. The differential cross sections are reported. 相似文献
17.
B. A. Kalin N. V. Volkov S. E. Sabo S. V. Zaitsev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(5):845-851
The results of studying the redistribution of Be, Al, Ti, Fe, Cu, Zr, Mo, and W atoms incorporated in polycrystalline metal
samples under irradiation with He+, (He+ + Ar+), and Ar+ ion beams with a broad energy spectrum and an average energy of 10 keV at irradiation doses of 1 × 1021 ion/cm2 are studied. It is discovered that irradiation at doses exceeding 1 × 1019 ion/cm2 results in local small-crystal formations being produced in a near-surface substrate layer. Their typical dimensions are
less than 1–5 μm, and their the density is up to 1–100. They contain incorporated atoms and impurity atoms with a concentration
of 0.1–10 at %. Subsequent irradiation at a dose of 1 × 1020 ions/cm2 or more leads to disappearance of these formations, mainly because of sputtering processes. 相似文献
18.
Total charge exchange cross sections were measured for He++ in He and Ar gas in the energy range from 50 to 540 eV using a single beam apparatus. For He++ in He the measured cross section is in agreement with calculations for symmetric resonant charge exchange. For He++ in Ar the cross section for charge exchange decreases with decreasing energy below 300 eV. The measured cross section suggests the formation of Ar+ ions to be more important at lower energies and the production of Ar++ to be dominant at higher energies. 相似文献
19.
V. M. Bystritsky V. V. Gerasimov J. Woźniak 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):79-84
The measurement method and results measuring of the stopping
power ratio of helium-3 and deuterium atoms for muons slowed down
in the D/3He mixture are presented. Measurements were performed
at four values of pure 3He gas target densities, ϕHe
= 0.0337, 0.0355, 0.0359, 0.0363 (normalized to the liquid
hydrogen density) and at a density 0.0585 of the D/3He mixture.
The experiment was carried out at PSI muon beam μE4 with the
momentum Pμ= 34.0 MeV/c. The measured value of the mean
stopping ratio S$_{3^He/D}$ is 1.66±0.04. 相似文献
20.
B. Pranszke S. Werbowy R. Miotk K. J. Borkowski A. Kowalski 《The European physical journal. Special topics》2013,222(9):2309-2315
Spectroscopic studies of collisions between He+ and He++ ions with H2 gas target have been performed in the 200–600 nm wavelength range. Atomic lines of hydrogen Balmer series and several helium lines were identified and their excitation functions between 50 eV and 1 keV (2 keV for He++) were determined. 相似文献