首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
A systematic study of the product((E(2_2~+)/E(2_1~+))*B(E2)↑) is carried out in the major shell space Z=50-82,N=82-126 within the framework of the asymmetric rotor model where the asymmetry parameter γ0reflects change in the nuclear structure.A systematic study of the product((E(2+)/E(2+))*B(E2)↑) with neutron number N is also discussed.The product((E(2_2~+)/E(2_1~+))*B(E2)↑) provides a direct correlation with the asymmetry parameter γ0.The effect of subshells is visible in Ba-Gd nuclei with N 82,but not in Hf-Pt nuclei with N 104.We study,for the first time,the dependency of the product((E(2_2~+)/E(2_1~+))*B(E2)↑) on the asymmetry parameterγ0.  相似文献   

2.
We obtain the asymptotic behaviour of the scattering amplitude when the pomeron has intercept α(0) larger than one. The reggeon field theory is studied by introducing a lattice in impact parameter space. Use is made of a previous result showing asymptotically the dynamics is controlled at each lattice site (α′ = 0 case) by a two-level structure. This leads to a non-Hermitean Hamiltonian expressed in terms of spin operators in which the intersite interaction terms is proportional to the pomeron slope α′. The spectrum of such a system shows a degenerate ground state for α(0) > αc >~ 1 and a continuum with vanishing excitation gap at α(0) = αc. The vacuum does not change structure at the critical value. The critically is shown by an order parameter which is given by the matrix element of a field operator between the vacuum and its degenerate companion. The nature of this critical phenomenon is better understood by continuously transforming the Hamiltonian into that of an Ising model with a transverse field which shows a well-known second-order phase transition. By defining the S-matrix so as to preserve the formal perturbation expansion, we find that for α(0) > αc, the zero gap state contributes a non-trivial asymptotic constant. The final asymptotic picture is that of a gray disc expanding like log s, so that the total cross section behaves as (log s)2. For α(0) < αC, the vacuum is non-degenerate and correspondingly the total cross section drops to zero as an inverse power of s.  相似文献   

3.
The stability of large Fröhlich bipolarons in the presence of a static magnetic field is investigated with the path integral formalism. We find that the application of a magnetic field (characterized by the cyclotron frequence ω c) favors bipolaron formation: (i) the critical electronphonon coupling parameter α c (above which the bipolaron is stable) decreases with increasing ω c and (ii) the critical Coulomb repulsion strength U c (below which the bipolaron is stable) increases with increasing ω c. The binding energy and the corresponding variational parameters are calculated as a function of α, U and ω c. Analytical results are obtained in various limiting cases. In the limit of strong electron-phonon coupling (α ? 1) we obtain for ω c ? 1 that E estim ? E estim(ω c = 0) + c(u)ω c/α 4 with c(u) an explicitly calculated constant, dependent on the ratio u = U/α where U is the strength of the Coulomb repulsion. This relation applies both in 2D and in 3D, but with a different expression for c(u). For ω c ? α 2? 1 we find in 3D E estim ? ω c - α 2 A(u) ln2(ω c/α 2), (also with an explicit analytical expression for A(u)) whereas in 2D E estim 2D ? ω c - αω cπ(u-2-√2)/2. The validity region of the Feynman-Jensen inequality for the present problem, bipolarons in a magnetic field, remains to be examined.  相似文献   

4.
An event with the decay chain Σc+Λc+ + π0, Λc+ → K? + p + π+, has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = ?ΔQ reaction v + p → μ? + p + K? + π+ + π+ + π0 with both gammas from the π0 decay detected. The proton and other final state particles are identified. The masses are M(Λc+) = 2290 ± 3 MeV/c2, M(Σc+) = 2457 ± 4 MeV/c2 and M(Σc+) ? M(Λc+) = 168 ± 3 MeV/c2. Including other data one obtains M (Σc++) ? M(Σc+) = 0 ± 4 MeV/c2.  相似文献   

5.
Data are presented and cross sections given for ф and f′ production in the channel K+p → K+pKK? at 10 Gev/c. The resonance parameters obtained from a fit to the KK? effective mass distribution are M = (1020.4 ± 0.5) MeV/c2 and Γ = (5.0 ± 1.3) MeV/c2 for the ф meson and M = (1514 ± 4) MeV/c2 and Γ = (28 ± 15) MeV/c2 for the f′. The resonance widths are corrected for experimental resolution. The branching fraction for the rate (ф → K01K02)/(ф → K+K) is determined to be 1.15 ± 0.15. The angular distributions for the decay of the f′ have unnormalized moments H(2,0) and H(4,0) different from the values for the nearby background, indicating spin 2 or greater for the f′.  相似文献   

6.
We review the methods of calculating the effective activation energy Ueff(T,B,J) for both transport measurements and magnetic decay, together with some theoretical models. Then, we apply these methods to our Hg-1223 single-phase superconductor to obtain the activation energy. Transport results give that the magnetic field and temperature dependence of the Ueff can be well described as U0B−α(1−T/Tc)m. Magnetic relaxation shows that the current density dependence of U(J) can be scaled onto a single curve, which can be considered as the activation energy at some temperature T0. The pinning mechanism in the measured temperature range does not change, and the activation energy depends separately on the three variables: T, B, and J, are responsible for the magnetic decay data scaling onto a single curve at various temperatures. As temperatures close to zero and near Tc, thermally assisted flux motion model is no longer valid since other processes dominate.  相似文献   

7.
A comparative study is made for Λc5He and Λc9Be charmed nuclei versus Λ5He and Λ9Be hypernuclei. The Λc(Λ)+α and Λc(Λ)+α+α systems are treated in a microscopic way. Within certain range of the ΛcN interaction strength, the energy properties of Λc+α and Λc+α+α are calculated and discussed. Similarity between the energy spectra of the noted charmed nuclei and hypernuclei is suggested.  相似文献   

8.
The 16O(d, α)14N, 14N(d, α)12C and 12C(d, α)10B reactions at Ed = 40MeV and the 12C(α d)114N at Eα = 55 MeV were investigated. A total of seventeen transitions are analysed in terms of one-step, zero-range DWBA calculations, using the two-particle coefficients of fractional parentage obtained from the Cohen-Kurath Op shell wave functions. For most transitions, fair agreement is obtained between experiment and calculation, possible exceptions being the transition to the Ex = 4.43 MeV, Jπ = 2+ state in 12C and to the Ex = 2.15 MeV, Jπ = 1+ state in 10B, for which the calculations predict too much L = 0 strength. Where possible, a comparison with previous (p, 3He) results is made. In 14N a state at Ex = 11.04 MeV was observed for which the values (Jπ; T) = (3+; 0) are suggested. In 12C we found, in addition to the well known T = 0 states, two relatively sharp T = 0 states at Ex = 19.50 ± 0.10 and 20.55 ± 0.10 MeV. The shape and strength of the angular distribution for the transitions to these states can be approximately accounted for by the calculations, although no one-to-one correspondence between observed and predicted levels could be established.  相似文献   

9.
The E-B (0g+-0u+) band system of Br2 has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range vE = 0–16, expressed in terms of the constants for 79Br2, are (in cm?1) Y0,0 = 49 777.962(54), Y1,0 = 150.834(22), Y2,0 = ?0.4182(28), Y3,0 = 6.6(11) × 10?4, Y0,1 = 4.1876(28) × 10?2, Y1,1 = ?1.607(16) × 10?4, and Y0,2 = 1.39(39) × 10?8. The bond distance is re = 3.194 A?, and the diabatic dissociation energy to Br+(3P2) + Br?(1S0) is 34 700 cm?1.  相似文献   

10.
吕燕南  黄祖洽 《物理学报》1989,38(9):1510-1514
采用显含电子对相关坐标的波函数,在微扰论的框架下计算了Elg+态氢分子与基态氢分子取cross构型时的中长程相互作用。结果表明,该相互作用在分子间距6.5α0附近存在着一个活化能势垒,在4.5α0附近显示出较强的化学键行为。 关键词:  相似文献   

11.
We present experimental data on the KL0p → KS0p reaction between 4 and 14 GeV/c in the range 0.1 ? |t| ? 2 GeV2. This experiment has been performed at the CERN PS, using spark chambers and a large aperture magnet. The results show a break of slope at t = ?0.3 GeV2. The ω trajectory deduced from the data has an intercept α(0) = 0.5 and a slope α′ = 0.88. A comparison with various models shows that the non-flip amplitude is dominant.  相似文献   

12.
Evidence for the quasi-elastic production of the doubly charged charmed barron Σ++c has been observed in a vp interaction in BEBC. The mass of the Σ++c and of its decay product, the Λ+c, are 2454±5 MeV and 2288±5 MeV, respectively. The mass difference M(Σ++c)? M(Λ+c) is 166±1 MeV. Combining the Λ+c mass value obtained here with the values obtained in the two Λ+c events previously observed in this experiment, thevalue M(Λ+c)=2283±3 MeV is deduced.  相似文献   

13.
Emission spectra of the b1Σ+(b0+)→X3Σ(X10+) transition of phosphorus iodide have been measured with a high-resolution Fourier-transform spectrometer. The PI radicals were generated and excited in a fast-flow system by reaction of phosphorus vapor (Px) with iodine and microwave-discharged oxygen. Four sequences, Δv=0,+1,−1,−2, of the b1Σ+(b0+)→X3Σ(X10+) transition of PI comprising 28 bands were observed. Six bands were measured at high spectral resolution. Vibrational and rotational analyses have yielded accurate spectroscopic constants of the X10+ and b0+ states (in cm−1): X10+: ωe=371.296(4), ωexe=1.3302(9), Be=0.1194117(2), αB=−0.0005676(7), De=4.56(2) ×10−8; b0+: Te=11136.921(4), ωe=400.165(6), ωexe=1.345(2), Be=0.1239237(2), αB=−0.0005540(2), De=4.84(5) × 10−8, where the numbers in parentheses are the standard deviations of the parameters. No emissions of the b0+X21 sub-system nor of the a1Δ(a2)→X3Σ(X21) transition have been observed leaving PI the only group Va halide for which the spin splitting in the X3Σ ground state is still unknown.  相似文献   

14.
Thep + np + diode is used to determine the hole drift velocity versus field curves in silicon as a function of temperature. By taking the analytical expression of the hole drift velocity,v=v m (E/E c )/(1+E/E c ),v m andE c are obtained in the temperature range from 210–420 K.v m varies from 1.04×107 cm/sec at 210 K to 1.11×107 cm/sec at 420 K, whileE c increases from 1.05×104 V/cm at 210 K to 5.3×104 V/cm at 420 K. The curve at 300 K is very close to the result of Norris and Gibbons.  相似文献   

15.
The paper presents the first report on χ(2) polarization induced in molecular glass of conjugated compound by all-optical poling. Transparent thin film of molecular glass of 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (BTAPVB) was prepared using a spin-cast technique. Dipolar as well as octupolar components in BTAPVB contributed to the formation of photoinduced χ(2) polarization. Growth rate of χ(2) polarization has good linear relation with Eω4E2ω, which suggested that the simultaneous processes of two-photon (ω + 2ω) and three-photon (ω + ω + ω) excitation on the same electronic level contributed to the formation of photoinduced χ(2) polarization.  相似文献   

16.
Emission spectra of the b1Σ+(b0+) → X3Σ(X10+,X21) and a1Δ(a2) → X21 transitions of AsBr have been measured in the near-infrared spectral region with a Fourier-transform spectrometer. The arsenic bromide radicals were generated in fast-flow systems by reaction of arsenic vapor (Asx) with bromine and were excited by microwave-discharged oxygen. The most prominent features in the spectrum are the Δv = +1,0,−1, and −2 band sequences of the b1Σ+(b0+) → X3Σ(X10+) transition in the range 11 700-12 700 cm−1. With lower intensities, the Δv = 0 and −1 sequences of the b1Σ+(b0+) → X3Σ(X21) sub-system show up in the same range. Further to the red, between 6000 and 6700 cm−1, the Δv = 0, +1, and −1 sequences of the hitherto unknown a1Δ(a2) → X21 transition are observed. Analyses of medium- and high-resolution spectra have yielded improved molecular constants for the X10+, X21, and b0+ states and first values of the electronic energy and the vibrational constants of the a2 state.  相似文献   

17.
A form factor F(t) for the pion is constructed which is compatible with analyticity and the data in the space-like and time-like region. For the mean square pion radius 〈r2〉 = (0.46?0.08+0.06) fm2 is obtained. Typical errors of the extrapolated F(t) are given (e.g. F(t =?8 GeV2/c2) = 0.07?0.10+0.04). Assuming F(t) ≈ β/(?t)α at the end of the space-like data region we obtain β = 0.31, α = 0.81 for t in GeV2/c2 together with the error contours of (α, β). No conclusive answer on the existence of zeroes of F(t) can be given.  相似文献   

18.
An optical-optical double-resonance technique has been applied to study the D(0u+) ion-pair state of Br2 in a one-photon resonant three-photon absorption. The OODR transition proceeds through the high vibrational level of the B3Π(0u+) state, which compromises a large Franck-Condon shift required for the excitation of Br2 from the X1Σg+ state to the D(0u+) state. Dunham parameters of the D(0u+) state, based on a global least-squares fit of 407 transitions (v′ = 0–16, J′ = 17–115), are Y00 = 49928.443(41), Y10 = 134.467(19), Y20 = ?8.71(27) × 10?2, Y30 = ?3.36(10) × 10?3, Y01 = 4.2382(15) × 10?2, Y11 = ?1.061(36) × 10?4, Y21 = ?2.00(27) × 10?6, and Y02 = ?1.93(11) × 10?8 for 79Br2 (all in cm?1, and 3σ in parentheses). The single rovibronic fluorescence spectrum of the D(0u+) state shows a transition terminating on the X1Σg+ ground state, and establishes the absolute v′ numbering on the basis of the Franck-Condon factor calculations. The v′ = 2 and 3 levels of the D(0u+) state are strongly perturbed due to the heterogeneous interaction with the 1u state correlating with the same ionic products of the D(0u+) state at the dissociation limit, Br?(1S) + Br+(3P2).  相似文献   

19.
The differential cross section for K±p elastic scattering has been measured in the very low t region (0.003 < t < 0.2 GeV2) in a wire chamber spectrometer experiment at 10.4 and 14 GeV/c. The interference effect observed between the Coulomb and the nuclear interaction has been used to determine α, the ratio of real to imaginary part of the forward scattering amplitude. At 10.4 GeV/c we measure α(K+p) = ?0.21 ± 0.06 and α(K?p = 0.08 ± 0.04, and at 14 GeV/c, α(K+p) = ? 0.13 ± 0.03 and α(K?p) = 0.000 ± 0.04 in agreeement with the predictions of dispersion theory calculation.  相似文献   

20.
A new optogalvanic technique with an rf discharge was applied to a high-resolution study of the Rydberg states of N2. The Ledbetter band, c4(0)1Πua″(0)1Σg+, and a new visible band, c5(0)1Σu+a″(0)1Σg+, were studied at a Doppler-limited resolution of 0.05 cm?1. A Doppler-free method was also applied to resolve overlapped lines. Precise wavenumbers were determined for the rotational transitions of the two Rydberg bands. The rotational and the centrifugal constants for the lowest Rydberg state, a″(0)1Σg+, were determined to be B0 = 1.913748(42) cm?1 and D0 = 6.088(99) × 10?6 cm?1, where the numbers in parentheses are the standard deviation and apply to the last digits.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号