共查询到20条相似文献,搜索用时 31 毫秒
1.
Ion cluster desorption yields from LiF were measured at PUC-Rio with ≈0.1 MeV/u N
q+ (q = 2,4,5,6) ion beams by means of a time-of-fight (TOF) mass spectrometer. A 252Cf source mounted in the irradiation chamber allows immediate comparison of cluster emissions induced by ≈65 MeV fission fragments
(FF). Emission of (LiF)
n
Li+ clusters are observed for both the N beams and the 252Cf fission fragments. The observed cluster size n varies from 1 to 6 for N
q+ projectiles and from 1 to ≈40 for the 252Cf-FF. The size dependence of the Y(n) distributions suggests two cluster formation regimes: (i) recombination process in the outgoing gas phase after impact and
(ii) emission of pre-formed clusters from the periphery of the impact site. The corresponding distribution of ejected negative
cluster ions (LiF)
n
F− closely resembles that of the positive secondary (LiF)
n
Li+ ions. The desorption yields of positive ions scale as Y(n) ∼ q
5. A calculation with the CASP code shows that this corresponds to a cubic scaling ∼S
e
3 with the electronic stopping power S
e
, as predicted by collective shock wave models for sputtering and models involving multiple excitons (Frenkel pair sputtering).
We discuss possible interpretations of the functional dependence of the evolution of the cluster emission yield Y(n) with cluster size n, fitted by a number of statistical distributions. 相似文献
2.
B. Cameron Reed 《Central European Journal of Physics》2005,3(1):1-7
The ground-state energy of neutral helium is estimated variationally with a trial wavefunction of the form ϕ≈e
−γ(rA/a
o)ne−γ(rB/a
o)n. This model represents a modification of traditional textbook examinations of this problem via inclusion of the power “n”
as a second nonlinear variational parameter in addition to the usual effective nuclear charge γ and leads to an upper-limit
on the ground state energy of −2.86107 E
h
(E
h
=1 hartree) in comparison with the traditional (n=1) result of −2.84766 E
h
. This result represents a reduction of the percentage overestimate from the true ground-state energy (−2.90373 E
h
) of from 1.93 to 1.47. In comparison with the maximum accuracy obtainable from an uncorrelated trial wavefunction, −2.86168
E
h
, the present trial wavefunction reduces the percentage overestimate from 0.49 (n=1) to 0.021. The optimum values of (n, γ)
are determined to be ≈(0.897, 1.825). 相似文献
3.
On the basis of quasipotential approach to the bound state problem in QED we calculate the vacuum polarization, relativistic,
recoil, structure corrections of orders α
5 and α
6 to the fine structure interval ΔE
fs = E(2P
3/2) − E(2P
1/2) and to the hyperfine structure of the energy levels 2P
1/2 and 2P
3/2 in muonic 23He ion. The resulting values ΔE
fs = 144 803.15 μeV, Δ$
\tilde E
$
\tilde E
hfs(2P
1/2) = −58 712.90 μeV, Δ$
\tilde E
$
\tilde E
hfs(2P
3/2) = −24 290.69 μeV provide reliable guidelines in performing a comparison with the relevant experimental data. 相似文献
4.
E. N. Elekina A. A. Krutov A. P. Martynenko 《Physics of Particles and Nuclei Letters》2011,8(4):331-336
On the basis of quasi-potential approach to the bound state problem in QED we calculate the vacuum polarization, recoil and
structure corrections of orders α5 and α6 to the fine splitting interval ΔE
fs = E(2P
3/2) − E(2P
1/2) in muonic 24He ion. The resulting value ΔE
fs = 146180.68 μeV provides reliable guideline in performing a comparison with the relevant experimental data. 相似文献
5.
A. V. Derbin S. B. Bakhlanov A. I. Egorov I. A. Mitropolsky V. N. Muratova D. A. Semenov E. V. Unzhakov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(4):481-486
We searched for resonant excitation of the first excited state of the 169Tm nucleus by axions formed inside the Sun by the Primakoff effect, A + 169Tm → 169Tm* → 169Tm + γ (8.41keV). Gamma quanta with an energy of 8.41keV were registered by a sectionalized Si(Li) detector installed in a
low-background setup. As a result, we set a new upper limit for the photon to axion coupling constant, g
Aγ
(GeV−1)m
A
(eV) ≤ 1.06 × 10−5, which for a hadronic axion model corresponds to a mass limit of m
A
≤ 169 eV at a 90% confidence level. 相似文献
6.
Corrections of order α
5 and α
6 to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear
structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, −1334.73
meV (1S), −166.64 meV (2S), −58 712.90 μeV (2P
1/2), and −24 290.69 μeV (2P
3/2), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of Δ12 = 8ΔE
hfs(2S) − ΔE
hfs(1S) = 1.59 meV can be used to test QED predictions. 相似文献
7.
Zhang XiaoAn Xiao GuoQing Yang ZhiHu Chen XiMeng Zhao YongTao Li FuLi Wang Li Cui Ying Zhang HongQiang Zhan WenLong 《中国科学G辑(英文版)》2008,51(1):82-89
Using the slow highly charged ions 129Xe
q+ (q = 25, 26, 27; initial kinetic T
0⩽4.65 keV/a.u.) to impact Au surface, the Au atomic Mα characteristic X-ray spectrum is induced. The result shows that as
long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even
though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10−8 and increases with the kinetic energy and potential energy of projectile. By measuring the Au Mα-X-ray spectra, Au atomic
N-level lifetime is estimated at about 1.33×10−18 s based on Heisenberg uncertainty relation.
Supported by the National Natural Science Foundation of China (Grant Nos. 10574132, 10274088 and 10405025), the Talent Introduction
Project of Xianyang Normal University (Grant No. 05XSYK103) and the Education Commission Foundation of Shaanxi Province (Grant
No. 04JK300) 相似文献
8.
The legume lectins are a large family of homologous carbohydrate-binding proteins. Their carbohydrate specificity and quaternary
structure vary widely. The carbohydrate binding activity of legume lectins depends on the simultaneous presence of calcium
and transition-metal ions, especially the Mn2+ ion. In the present work, thermal stabilities of Mn2+ binding sites in pea, lentil, soybean and kidney-bean lectins have been studied by electron spin resonance spectroscopy in
the temperature range of 120–400 K in different atmospheres. The evolution of parameters, such as the line width, peak-to-peak
intensity associated with the hyperfine transition [m
I
(+5/2) → m′
I
(−5/2)] at the lowest magnetic field side of the central electron transition [m
S
(+1/2) → m′
S
(−1/2)] of the Mn+2 ion, g-factor and hyperfine splitting was evaluated. Annealing was also performed at high temperatures (353, 373, 383, 403 and 443
K) and the oxidation activation energy of Mn2+ ions in the indicated legumes was determined. 相似文献
9.
A. Korgul H. Mach B. A. Brown A. Covello A. Gargano B. Fogelberg W. Kurcewicz E. Werner-Malento R. Orlandi M. Sawicka 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):25-29
Recently the first excited state in 135Sb has been observed at the unexpectedly low excitation energy of only 282keV and interpreted as mainly d
5/2 proton coupled to the 134Sn core. Based on theoretical considerations it was suggested that its low excitation energy is related to a relative shift
of the proton d
5/2 and g
7/2 orbits induced by the neutron excess. We have measured the lifetime of the 282keV state by the advanced time-delayed βγγ(t) method. The measured half-life, T
1/2 = 6.1(4)ns, yields exceptionally low limits of B(M1;5/21
+→7/21
+)≤3.0×10-4
μ
2
N and B(E2;5/21
+→7/21
+)≤54e
2
fm
4. These strongly hindered M1 and slow E2 transition rates are similar to those for the transition de-populating the first excited state at 405keV in 211Bi. Results of shell model calculations with realistic interactions are presented. The M1 decay rate was found to be extremely sensistive both to the wave function and to the M1 effective operator. 相似文献
10.
The torus group (S
1)ℓ+1 has a canonical action on the odd-dimensional sphere S
q
2ℓ+1. We take the natural Hilbert space representation where this action is implemented and characterize all odd spectral triples
acting on that space and equivariant with respect to that action. This characterization gives a construction of an optimum
family of equivariant spectral triples having nontrivial K-homology class thus generalizing our earlier results for SU
q
(2). We also relate the triple we construct with the C
*-extension
相似文献
11.
A standard partial-wave analysis was performed on the basis of known measurements of differential cross sections for elastic
p
13C scattering at energies in the range 250–750 keV. This analysis revealed that, in the energy range being considered, it is
sufficient to take into account the 3
S
1 wave alone. A potential for the triplet 3
S
1-wave state of the p
13C system in the region of the J
p
T = 1−1 resonance at 0.55 MeV was constructed on the basis of the phase shifts obtained from the aforementioned partial-wave analysis. 相似文献
12.
Zhong Liu Yuhu Zhang Yingjun Ma Y. Sasaki K. Yamada H. Oshima H. Yokose M. Ishizuka T. Komatsubara K. Furuno 《中国科学G辑(英文版)》2003,46(4):390-397
Excited states of125Sb have been studied using in-beam γ spectroscopy techniques via the124Sn(7Li, α2n) reaction at a beam energy of 32 MeV. A high-spin level scheme including 21 new γ-transitions and 14 new excited states
have been established. Three isomers have been identified at 1970, 2110 and 2471 keV and the ranges of their half-lives have
been estimated from the delayed coincidence data. The level structure of125Sb is discussed in terms of particle-core excitation coupling. With the help of empirical shell model calculations the three
isomers are proposed to have three-quasiparticle πg7/2⊗v(h
11/2
s
1/2)5−, πg7/2⊗v(h
11/2
d
3/2)7− and πg7/2⊗v(h
112/2)10
+ configurations, respectively. 相似文献
13.
Within the framework of the single-channel approximation, an {αtd} model of the 9
Be nucleus is presented. A comparative analysis of the t 6
Li wave functions describing relative motion of bound states constructed in {ααn} and {αtd} cluster representations is carried out on the example of calculations of the 9
Be(γ,t0)6
Li process characteristics.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 85–89, January, 2008. 相似文献
14.
Duan’s simple model is extended to analyze the mixing of the 4f
N − 15d configuration with the 4f
N
states. The explicit static coupling and traditional dynamic coupling are considered, and the parameters are fitted according
to the absorption spectrum in LiYF4: Nd3+. The parameter values obtained are as follows: T
32 = −28i × 10−7, T
52 = −1151i × 10−7, A
322 = 192i × 10−12 cm, A
524 = i × 10−12 cm, A
726 = 54i × 10−12 cm, and A
766 = −680i × 10−12 cm. Compared to the experimental measurements, the present model yields better results than those obtained from the Judd-Ofelt
theory.
The text was submitted by the authors in English. 相似文献
15.
N. Burtebayev S. V. Artemov B. A. Duisebayev Zh. K. Kerimkulov S. B. Kuranov S. B. Sakuta 《Physics of Atomic Nuclei》2010,73(5):746-756
At an energy of 25 MeV and in the angular range 7°−175° in the laboratory frame, angular distributions were measured for elastic
deuteron scattering on 6Li nuclei and for the respective inelastic-scattering processes accompanied by the transitions to the ground state (1+) of
the 6Li nucleus and to its excited state at E
x
= 2.186 MeV (J
π = 3+). The resulting data were analyzed on the basis of the optical model of the nucleus and the coupled-reaction-channel method
with allowance for the mechanism of alpha-particle-cluster exchange. It is shown that only upon including, in the analysis,
channel coupling and the exchange mechanism can the experimental cross sections for elastic and inelastic scattering be reproduced
over the entire range of angles. 相似文献
16.
K P SANTHOSH 《Pramana》2011,76(3):431-440
Decay of neutron-deficient 128 − 137Gd parents emitting 4He to 32S clusters are studied within the Coulomb and proximity potential model. The predicted half-lives are compared with other
models and most of the values are well within the present experimental limit for measurements (T
1/2 < 1030 s). The lowest T
1/2 value for 28Si emission from 128Gd indicates the role of doubly magic 100Sn daughter in cluster decay process. It is also found that neutron excess in the parent nuclei slows down the cluster decay
process. Geiger–Nuttal plots for all clusters are found to be linear with different slopes and intercepts. The α-decay half-lives of 148 − 152Gd parents are computed and are in agreement with experimental data. The role of doubly magic 132Sn daughter in cluster decay process is also examined for various neutron-rich Ba, Ce, Nd, Sm and Gd parents emitting clusters
ranging from 4He to 32Si. Alpha-like structures are most probable in the decays leading to 100Sn, while non-α-like structures are probable in the decays leading to 132Sn. The neutron–proton asymmetry in parent and daughter nuclei is responsible for the reduced decay rate in the decay leading
to 132Sn. 相似文献
17.
I. V. Glavanakov P. Grabmayr Yu. F. Krechetov A. N. Tabachenko 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):747-749
Experimental research on positive-pion photoproduction on the oxygen nucleus in the 16O(γ, π+p) reaction at high recoil momenta of the residual nuclear system was performed. The yield for the 16O(γ, π+p) reaction was analyzed using a model that takes Δ-isobar configurations in nuclei ground states into account, together with
the earlier-measured yield of the12C(γ, π+p) reaction. The estimated number of isobars per nucleon N
Δ = 0.012 ± 0.005 was obtained for the 12C nucleus, and 16O N
Δ = 0.018 ± 0.004 was obtained for the 16O nucleus. 相似文献
18.
The vibration frequencies of unstable ferroelectric and antiferrodistortion modes and the dependences of the energy on the
ion displacement amplitude have been calculated within the generalized Gordon-Kim model for distortions along eigenvectors
of these modes in the mixed compounds Sr1 − x
A
x
Ti1 − x
/4□
x/4O3 and Sr1 − y
A
2y
/3□
y/3TiO3 (A = Sc3+, In3+, La3+, Bi3+; □ is the vacancy). To compensate an excess positive charge, vacancies are introduced into the Ti4+ or Sr2+ site. Calculations have been performed in the “daverage” crystal approximation for impurity concentrations of 0.25 and 0.50.
To this end, a set of 40 atomic superlattices with various orderings of heterovalent ions Sr2+ and impurity A
3+ has been considered. It has been found that each impurity type, independently of charge balance, induces ferroelectric instabilities
in doped compounds. In the case of doping with In3+ and La3+ for concentration x = 0.25, the possibility of rotating the polarization vector has been shown. 相似文献
19.
Doubly-charged scalars, predicted in many models having exotic Higgs rep-resentations, can in general have lepton-number violating
(LFV) couplings. We show that by using an associated monoenergetic final state photon seen at a future linear e
−
e
− collider, we can have a clear and distinct signature for a doubly-charged resonance. The strength of the ΔL = 2 coupling can also be probed quite effectively as a function of the recoil mass of the doubly-charged scalar.
相似文献
20.
Hyperfine splittings (HFS) are calculated within the Field Correlator Method, taking into account relativistic corrections.
The HFS in bottomonium and the B
q
(q = n, s) mesons are shown to be in full agreement with experiment if a universal coupling α
HF = 0.310 is taken in perturbative spinspin potential. It gives M(B*) −M(B) = 45.7(3) MeV, M(B
s
* ) − M(B
s
) = 46.7(3) MeV (n
f
= 4), while in bottomonium ΔHF(b
$
\bar b
$
\bar b
) = M(Υ(9460)) − M(η
b
(1S)) = 63.4 MeV for n
f
= 4 and 71.1 MeV for n
f
= 5 are obtained; just the latter agrees with recent BaBar data. For unobserved excited states we predict M(Υ(2S))−M(η
b
(2S)) = 36(2)MeV,M(Υ(3S))−M(η
b
(3S)) = 28(2)MeV, and also M(B
c
*) = 6334(4) MeV, M(B
c
(2S)) = 6868(4) MeV, M(B
c
* (2S)) = 6905(4) MeV. The mass splittings between D(23
S
1) − D(21
S
0), D
s
(23
S
1) − D
s
(21
S
0) are predicted to be ∼75 MeV, which are significantly smaller than in several other studies but agree with the mass splitting
between recently observed D(2533) and D*(2610). 相似文献