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1.
A new theory of the ground state energy of a two-dimensional electron fluid is presented. It is shown that the ring diagram contribution changes its analytical behavior atr s =21/2, wherer s is the usual density parameter defined by rS = 1/a 0( n)1/2,a 0 being the Bohr radius andn is the electron density. For smallr s , a high density series is obtained in agreement with the previous calculation. For larger s , a hitherto unknown low density series is obtained. In the low density region, the first order exchange energy is completely cancelled out by a term from the ring contribution so that the ground state energy decreases in proportion tor s –2/3 , followed byr s /–4/3 and higher order terms. The energy is found to be minimum atr s=1.4757, the minimum value being –0.481915 Rydbergs.  相似文献   

2.
Analytical expressions for the binding energy of electrons and positrons in dielectric clusters, analyzed in this work, neglect the elastic effects. Therefore, we present the density-functional theory for neutral liquid clusters that experience the spontaneous deformation. Using the 1/R-expansion, R being the cluster radius, the exact analytical expressions for the size corrections to the chemical potential, surface tension, and atomic density are derived from the condition of mechanical equilibrium. The problem of calculating these corrections is reduced to calculating the quantities for a liquid with a flat surface. The size compression and tension of density occur in the 1/R and 1/R 2 orders respectively. The sizes of charged rigid and elastic critical clusters, for which the electron or positron binding energy is close to zero, are calculated for Xe N ? , Kr N ? , Ar N ? , Ne N + , He N + . The calculations show significant contribution of self-compression to the binding energy of the excess electron in contrast to the positron.  相似文献   

3.
The contributions of the superposition of configurations ns 25d 76s+ns5d 76sn′s+ns5d 76s 2 (n=1–5, n′=7–10) to the parameters of the hyperfine structure a 5d 01 , a 5d 12 , a 5d 10 , a 6s 10 in the spectrum of the osmium atom Os I are calculated. Nonzero contributions are shown to be made only to the parameters a 5d 10 and a 6s 10 . This fact justifies the inclusion of the parameter a 5d 10 in the semiempirical analysis of experimental values of magnetic dipole constants of the hyperfine structure of the 5d 7 s configuration in the spectrum of the osmium atom. The effect of nucleus volume on the parameters of the hyperfine structure in the spectra of osmium isotopes 187Os and 189Os is estimated.  相似文献   

4.
We attempt to impose elastic unitarity on the forward π-π scattering using the Veneziano Amplitude together with a crossing symmetric subtraction term as an input. TheN/D method is used and thep, ? mesons are interpreted as CDD poles. The self consistency requirement led to the evalutation of the low energy parameters and theS andP-wave phase shifts. The values of the scattering lengths obtained area 0 0 =0.084m π ?1 ,a 2 0 =?0.024m π ?1 ,a 1 1 =0.047m π ?3 .  相似文献   

5.
Results are presented on two-particle inclusive production inK + p interactions at 32 GeV/c. We study thex 1,2=x 1+x 2 dependence of invariant structure functions of (ππ)-pairs and compare them to single particle inclusive distributions in the fragmentation regions. Distributions of particles observed at Feynmanx 2 in association with various “trigger” particles or systems atx 1 in the same hemisphere are dicussed in terms of the reduced variable \(\tilde x_2 = x_2 /(1 - |x_1 |)\) . We further present absolute production rates and production ratios of π+'s and π?'s associated with π±,K s 0 , Λ, \(\bar \Lambda \) ,K *+ (890), (K s 0 π+), and (π+ π?)-triggers, and compare them with qualitative predictions of the quark recombination model. Forwardbackward correlations between (K s 0 π±), (K s 0 ,p), (Λ, π?), \((\bar \Lambda \pi ^ \pm )\) , and (p, π?) pairs are also discussed.  相似文献   

6.
The inclusive cross section for the production ofK s 0 mesons, Λ and \(\bar \Lambda\) particles in proton-proton interactions at \(\sqrt s = 63\) GeV is presented. The produced particles have been detected in the full phase space. Behaviour of the longitudinal and transversal depandences of the cross sections are discussed. The total production cross sections for s 0 mesons and Λ particles was determined to \(\sigma _{{\rm K}_S^0 } = (25.5 \pm 1.4)\) mb andσ Λ =(7.8±1.2) mb respectively. A strong energy dependence of the production cross sections is observed.  相似文献   

7.
The new experiment planned at Brookhaven to measure the anomalous magnetic moment of the muona μ≡(g μ?2)/2 will improve the present accuracy of 7 ppm by about a factor of 20. This requires a careful reconsideration of the theoretical uncertainties of theg?2 predictions, which are dominated by the error of the contribution from the light quarks to the photon vacuum polarization. This issue is cruicial also for the precise determination of the running fine structure constant at theZ-peak as LEP/SLC experiments continue to increase their precision. In this paper we present an updated analysis of the hadronic vacuum polarization using all presently availablee +e? data. This seems to be justified because previous work on the subject was based to some extent on preliminary or incomplete experimental data. Contributions from different energy ranges are presented separately forg?2 of the muon and the τ-lepton and for α(M Z 2 ). We obtain the resultsa μ had* =(725±16)×10?10 anda τ had* =(351±10)×10?8, where the asterisk indicates the dressed (renormalization group improved) value. For the effective fine structure constant atM Z=91.1888 GeV we obtainΔα had (5) =0.0280±0.0007 and α(M Z 2 )?1=128.896±0.090. Further improvement in the accuracy of theoretical predictions which depend on the hadronic vacuum polarization requires more precise measurements ofe +e? cross-sections at energies below about 12 GeV in future experiments.  相似文献   

8.
The ratios of the radiative transition probabilities for the lines of the P, Q, and R branches of the (4d)r 3Π g ? , (4d)s 3Δ g ? → (2p) c 3Π u ± band systems of the H2 molecule have been measured for the first time. Significant (to two orders of magnitudes) differences are found between the experimental values and the adiabatic theory predictions. It is established that the results of the nonadiabatic calculation performed by us in the pure-precession approximation taking into account the electronic-rotational interaction of the 4d 3Πg and 4d 3Δg states are in agreement with the experimental data. The optimal energies of rovibronic levels of the r 3Π g ? , s 3Δ g ? , c 3Π u ? , and c 3Π u + states have been found and reidentification of 11 from 54 spectral lines, assigned previously to the (0-0) and (1-1) bands, was performed.  相似文献   

9.
Preliminary results from the correlation femtoscopy of identical kaons in the SELEX experiment (Fermilab E781) are presented. Kaons are selected in inclusive reactions of Σ?C(Cu) interactions at an initial energy of 610 GeV. Kaon pairs are studied in all possible charged states: K s 0 K s 0 , K s 0 K+, K s 0 K?, K+K+, K+K? and K?K?. The source sizes of the hadronization region of neutral and charged kaon pairs are measured.  相似文献   

10.
The spin wave Green function of a random dilute Heisenberg ferromagnet is calculated by the Molecular CPA method for the bond model of the f.c.c. lattice. It is found that the ferromagnetic spin order atT=0 becomes unstable, if the concentration of the non-zero bondC A decreases below the critical valueC A 0 =0.1702, which is some-what larger than the percolation concentrationC A P =0.125. In the regionC A <C A 0 , aδ function spectrum appears atE=0 corresponding to the free rotations of the total spins of the finite clusters. The peculiar structure of the spin wave state density near the critical concentration is analysed in detail and a speculation is made for the topological structure of the spin clusters.  相似文献   

11.
InclusiveK s 0 andK s 0 K s 0 production in \(\bar pp\) interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c are studied. Cross sections ofK s 0 , K s 0 K s 0 andK (892) are presented for each incident momentum. The production ofK s 0 andK (892) through annihilation process is investigated. It is found that the annihilation process is dominant but decreases with incident momentum. The annihilation process is compared withe + e ? interactions. Remarkable similarity between them is found in the \({{x_0 = 2E(K_s^0 )} \mathord{\left/ {\vphantom {{x_0 = 2E(K_s^0 )} {\sqrt s }}} \right. \kern-0em} {\sqrt s }}\) distribution. Events with two detectedK s 0 's are analyzed. The result shows theK s 0 K s 0 pairs are produced in the central region of c.m. system and there is a clearS * signal in theK s 0 K s 0 effective mass distribution.  相似文献   

12.
A separable representation of theS-wave Paris potential and a phase-shift equivalent Yamaguchi-type potential significantly differing in their off-shell behaviours are used to calculate second-order polarization observables of elastic nucleon-deuteron scattering atE D=10 and 20MeV. Off-shell effects are found that stem from differences in the nuclear interaction in the inner regionr?1.2 fm. Adding approximate Coulomb-distortion contributions to the purely nuclear Faddeev amplitudes proton-deuteron predictions are obtained. Coulomb effects are not found to be negligible. Comparison with experimental data, in particular, the spin-correlation parameterC y,y of the reaction \({}^1\vec H(\vec d,d)^1 H\) forE D=10MeV vector-polarized deuterons and the spin-transfer coefficientsK y y′ ,K x x′ andK z x′ for \({}^2H(\vec p,\vec p)^2 H\) atE p=10MeV, prefer the interaction model that contains an intermediate-range repulsion.  相似文献   

13.
It is numerically shown that the groundstate of the Friedel problem (consisting of a conduction band and a dresonance), occupied with (n+ 1) electrons, can be written as Ψ = (A a 0 * +Bd*) Π v=1 n a v * Φ0, where a 0 * represents a localized conduction electron state, d* is the Friedel resonance state and Π v=1 n a v 8 Φ0 is a Slater determinant of n single electron states a t * , (Φ0 is the vacuum state). The a i * together with a 0 * are part of a full ortho-normalized basis of the conductions band.  相似文献   

14.
A method of simultaneous parametrization of one- and two-body interactions on atomic hyperfine structure of configurationl N is proposed and applied for the analysis of the configuration (6p)3 in the bismuth atom. For this purpose, the hyperfine structure splittings of the levels2D 3 2/0 ,2D 5 2/0 and2P 1 2/0 were measured. The finally obtained values of HFS parameters are: for one-body parameters (in MHz):a p 01 =2,537(9),a p 12 =5,182 (12),a10=?2,019(10),b p 02 =?3,198(53),b p 11 =2,816(54); for two-body parameters (in MHz):x pp ′/01 ,2=284(3),x pp ′/12 ,2=581(5),x pf ′/12 ,2=170(70),x pp ′/02 ,2=?359(36),x pf ′/02 ,2=?33(100). The value of the quadrupole moment of the nucleus 83 209 Bi is also discussed.  相似文献   

15.
Using the204Hg(α, pn)-reaction andα-particles of energies 39–55 MeV, we have found an isomeric 3.6 min 12? state in206Tl at 2,642.9 keV which has the two-hole configurationπh 11 2/?1 vi 13 2/?1 The 12? state decays mainly by anE5 transition of energy 1,021.4 keV to a 7+ state at 1,621.5 keV whose main configuration isπs 1 2/?1 vi 13 2/?1 There is, in addition, evidence for a weak 565 keVM 4 branch to an 8+ state at 2,078 keV whose main configuration should beπh 11 2/?1 vf 5 2/?1 . The 7+ state decays by a stretched cascade ofγ-rays to states of the following values ofJ π and excitation energy: 5 ? + , 1,405.4 keV; 4?, 952.1 keV; 2?, 265.8 keV and 0?, 0 keV. The main configurations of these states areπh 11 2/?1 vp 1 2/?1 ,πd 3 2/?1 vf 5 2/?1 ,πd 3 2/?1 vp 1 2/?1 andπs 1 2/?1 vp 1 2/?1 respectively. From the nuclear masses of208Pb,207Pb,207Tl, and206Tl and the experimental excitation energies it is possible to obtain the proton hole-neutron hole interaction in206Tl. This interaction is compared with the calculations of Kuo and Herling and the discrepancies are discussed. The 12?→8+ M4 transition rate is reduced because of destructive interference between the protonh 11/2d 3/2 and the neutroni 13/2f 5/2 contributions. The magnitude of the reduction is accurately reproduced by the wave functions of Kuo and Herling. The 12?→7+ E5 transition rate is about twice as large as the single-holeπh 11 2/?1 πs 1 2/?1 transition rate. This deviation is fully explained by the configuration admixtures in the 7+ state, given by Kuo and Herling.  相似文献   

16.
A comparative study is made of four three-parameter semiempirical potential energy functions for 32 electronic states of diatomic molecules and their ions:n 2:X1gS g + ,B 3πg,A 3 gSu,C 3 u,B′ 3 gSu.a 1 πg, a′gS u ? ,Ω 1δu N 2 + :X 2 gS g gS +A 2 π,C 2 gS u + ,B 2 gS u + CO:X1gS+,a 3 π, a′3 gSu,e 3 gS?,d 3gD1,A 1π CO+:X2gS+,A 2 π,B 2gS+ O2:X3gS g ? ,B 3 gSu,c 1 gS u ? ,b 1gS g s ,a 1 δg,c 3 δu O 2 + :X 2πg,A 2 πg, a1 πg,b 4 gS g ? A program for numerically integrating the radial Schrödinger equation by the Cooley method is worked out. Certain additional units are introduced to conserve computer time. The resulting vibrational levels are compared with the experimental levels for all the electronic states studied. It is concluded on the basis of this analysis that it is not possible to describe equally well all the electronic states of various molecules on the basis of any single three-parameter potential function. A method for choosing a potential function for describing some particular electronic state of a diatomic molecule is proposed.  相似文献   

17.
To help the difficult determination of the angle γ of the unitarity triangle, Aleksan, Dunietz and Kayser have proposed the modes of the typeK ? D s + , common toB s and $\bar B_s $ . We point out that it is possible to gain in statistics by a sum over all modes with ground state mesons in the final state, i.e.K ? D s + ,K *? D s + ,K ? D s *+ ,K * D s * . The delicate point is the relative phase of these different contributions to the dilution factorD of the time dependent asymmetry. Each contribution toD is proportional to a product $F^{cb} F^{ub} f_{D_s } f_K $ whereF denotes form factors andf decay constants. Within a definite phase convention (i.e. for example the one defined by the heavy quark symmetry in the limit of heavy quarks), lattice calculations do not show any change in sign when extrapolating to light quarks the form factors and decay constants. Then, we can show that all modes contribute constructively to the dilution factor, except theP-waveK * D s *+ , which is small. Quark model arguments based on wave function overlaps also confirm this stability in sign. By summing over all these models we find a gain of a factor 6 in statistics relatively toK ? D s + . The dilution factor for the sumD tot is remarkably stable for theoretical schemes that are not in very strong conflict with data onB→ψK(K *) or extrapolated from semileptonic charm form factors, givingD tot≥0.6, always close toD(K ? D s + ).  相似文献   

18.
Contributions of the superposition of configurations ns 25d 8+ns5d 8 n′s (n=1–5, n′=6–10) and ns 25d 6+ns5d 6 n′s (n=1–6, n′=7–10) to parameters a 5d 01 , a 5d 12 , and a 5d 10 of the hyperfine structure in the spectrum of the osmium atom OsI are calculated. It is shown that the nonzero contribution is made only to a 5d 10 . The effect of the spatial distribution of nuclear charge on the parameters of the hyperfine structure in the spectra of 187Os and 189Os isotopes and on the hyperfine anomaly for the 5d 76s levels in the spectrum of these isotopes is estimated.  相似文献   

19.
Starting from an isospin invariant shell-model hamiltonian, we describe a method for deriving microscopically the IBM-hamiltonian appropriate to lights d-shell nuclei. The key ingredients of our approach are:a) the Belyaev-Zelevinsky-Marshalek (BZM) bosonization procedure;b) two successive unitary transformations that extract the “maximally decoupled” collective bosons with angular momentaJ=0(s ππ + ,s νν + ,s πν + ) andJ =2(d ππ + ,d νν + ,d πν + (T=0),d πν + (T=1)). The method is applied to obtain the low-energy spectra and the electron scattering form factors for the 0 1 + →2 1 + transitions in20Ne and24Mg. Good agreement with the exact shell-model results is achieved. The inclusion of proton-neutron bosons (s πν + ,d πν + (T=1),d πν + (T=0)), as well as the renormalization of boson parameters due to the non-collective degrees of freedom, are shown to play a crucial role.  相似文献   

20.
The kinetics of the reaction of CH 3 + ions with N2O and NH3 has been investigated in He and Ar buffers using Selected Ion Flow Drift Tube technique (SIFDT). Both studied reactions proceed with nearly collisional rate at near thermal energies. The rate coefficient of the reaction of CH 3 + with N2O is decreasing more than one order of magnitude (from 1.2×10?9cm3s?1 up to 8×10?11cm3s?1) with reactant ion/reactant neutral average centre-of-mass kinetic energy (E r) increasing from near thermal up to 2 eV. The dominant product of this reaction is the isomer HCO+ (≥94%) and the minor product is CH3O+. The reaction of CH 3 + with NH3 has two binary channels with the dominant product ion CH2NH 2 + (>70%) and the minor product ion NH 4 + (≈10%) and three body association channel with product CH3NH 3 + (≈20% at 0.32 Torr). The rate coefficient of this reaction is decreasing nearly by one order of magnitude with increasingE r from near thermal up to 0.8eV, forE r>0.8 eV the rate coefficient increases with increasingE r. The experimental results are interpreted in terms of a simple model assuming the reactions to proceed via the formation of long-lived collision complexes.  相似文献   

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