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1.
Data were taken at the energy 2E = 990 MeV to search for multibody events, with the same large solid angle detector which has been used for the measurement of the , ω andφ production by e+e annilations. Assuming a π+ππ0π0 production by the quasi two-body process e+e → → ωπ0 we give the correspondi ng cross section σ(e+e → π+ππ0π0) = (1.1 ± 0.5) 10−32 cm2. Since no events with 3 and 4 charged pions have been observed σ(e+e → π+ππ0π) 1.5 × 10−33 cm2.  相似文献   

2.
Six rotational bands in the odd-odd nucleus 174Ta have been populated with the 160Gd(19F,5n) reaction. High-spin states were identified using the NORDBALL array. Both signatures of the doubly decoupled π1/2 [541] ν1/2 [521] band and semi-decoupled π1/2 [541] ν7/2 [633] band are observed, in addition to the high-K couplings of the π9/2 [514] ν7/2+ [633], π9/2 [514] ν5/2 [512], π7/2+ [404] ν7/2+ [633], and π5/2+ [402] ν5/2 [512] configurations. The signature splitting of the π1/2 [541] ν7/2+ [633] band is inverted from the expected splitting, and this is interpreted as being due to a residual proton-neutron interaction. It is shown empirically that this interaction, together with deformation changes, can account for the increased crossing frequency associated with the alignment of i13/2 neutrons in the π1/2 [541] bands of odd-Z nuclei.  相似文献   

3.
The third-order nonlinear optical response of a triphenylmethane dye (Acid blue 7) was studied using the Z-scan technique with a continuous-wave He–Ne laser radiation at 633 nm. The magnitude and sign of the third-order nonlinear refractive index n2 of aqueous solution of Acid blue 7 dye were determined; the negative sign indicates a self-defocusing optical nonlinearity in the sample studied. The negative nonlinear refractive index n2 and nonlinear absorption coefficient β were estimated to be −1.88 × 10−7 cm2/W and −3.08 × 10−3 cm/W, respectively, corresponding to Re(χ(3)) = −8.35 × 10−6 esu, and Im(χ(3)) = −6.88 × 10−7 esu. The experimental results show that Acid blue 7 dye have potential applications in nonlinear optics.  相似文献   

4.
We derived an empirical relationship between |χ(3)| and absorption spectra based on a simple two-level model. We calculated third-order nonlinear susceptibility for a methanol solution of rose bengal (RB), a polydiacetylene thin film (PDA), and a GaAlAs/ GaAs multiple quantum well (MQW) using the relationship. The estimated values are of the same order as the experimental ones. We also investigated the effect of the sharpening absorption bandwidth on |χ(3)| enhancement, and found that |χ(3)| of 10−6 esu can be expected if the width of the PDA absorption band is reduced by one order of magnitude.  相似文献   

5.
The reactions πp → 2ππ+p, πp → 2ππ+πop and πp → 2π+n are analysed at 11 and 16 GeV/c using longitudinal phase space (LPS) plots. The weighted LPS distributions for πp → 2ππ+p is dominated by two well separated structures corresponding to single diffraction dissociation of the pion, πp → (2ππ+)p, and of the proton, πp → ππ+p). The former is more abundant than the latter, and both are approximately constant with energy. In contrast, processes of type πp → (2π)(πp) decrease with increasing energy.

In the five-body reactions the weighted LPS distribution reveals especially at 16 GeV/c a maximum for single dissociation of the proton into 3πp, namely πp → ππ+πop); this process is likely to be diffractive. The neutron channel has a corresponding maximum displaced toward a multiperipheral configuration πp → π+)n. Another strong maximum corresponds to the pion dissociation πp → (2ππ+πo)p. This is interpreted to be an ω-exchange process because no analogous structure occurs in πp → (2π+)n. Finally, a broad structure reveals double dissociation of both incident particles; it occurs in the two channels πp → (2ππ+)(πop) and πp → (2ππ+)(π+n), being stronger in the latter. Further analysis of this process in terms of isospin exchange suggests that it is partially diffractive. Factorization is also discussed.

An appendix gives general aspects of the LPS analysis for the asymptotic study of n-body collisions at very high energy.  相似文献   


6.
The emission of two photons above 25 MeV energy was observed in the capture of stopped pions by beryllium and carbon with a rate of (1.0 ± 0.1) × 10−5, respectively (1.4 ± 0.2) × 10−5 per capture. These rates are about two to four times greater than various free-nucleon estimates based on the π+→γγ annihilation mechanism alone.  相似文献   

7.
The time-dependence of the decay rate of initially pure K0 into the final state (π+ππ0) has been studied in search for the decay kS0→π+ππ0. No evidence is found in a sample of 384 observed events. The ratio of the CP -violating KS0 amplitude and the KL0 amplitude is η+−0 = (0.13−0.20+0.17) + i(0.17−0.26+0.27); the ratio of the CP-conserving KS0 amplitude and the KL0 amplitude is < 0.4. The energy dependence of the K0→π+ππ0 matrix element is found to be a+−0 = −0.31 ± 0.03.  相似文献   

8.
Toshimitsu Yamazaki   《Nuclear Physics A》2000,670(1-4):157-164
A new type of nuclear spectroscopy to study hadron-nucleus bound states is described. The first successful experiment was to search for deeply bound π states in heavy nuclei using the 208Pb(d,3He) reaction at GSI, in which a narrow peak arising from the 2p π orbital coupled with the neutron-hole states was observed at 135 MeV excitation energy. An improved experiment has just been carried out to separately identify the 1s and 2p π states. These experiments provide important information on the local potential strength, from which the effective mass of π is deduced to be 20 MeV. This method will be extended to search for η and ω bound states as well as for K bound states. The advantage of the bound-state spectroscopy versus invariant mass spectroscopy is emphasized.  相似文献   

9.
Reversible and irreversible domain wall (DW) motions have been investigated in La0.7Sr0.3MnO3 ceramic samples using frequency-response complex permeability with various amplitudes of AC field. We also examine the effects of temperature in the range from 293 to 368 K and transverse DC magnetic field with a maximum of 4.40×105 A/m on the real part of permeability (μ′). Two relaxations corresponding to reversible wall motions and domain rotations occur in low and high frequency regions, respectively. The irreversible DW displacements can be activated as the amplitude larger than the pinning field of 3 A/m, leading to an increase in μ′. The μ′ obeys a Rayleigh law at the temperature below 343 K or under DC field of less than 4.22×104 A/m. The Rayleigh constant η increases from 5.45×10−2 to 1.54×10−1 (A/m)−1 as the temperature rises from 293 to 343 K, and η decreases from 5.58×10−2 to 3.67×10−2 (A/m)−1 with increasing DC field from 1.99×103 to 4.22×104 A/m.  相似文献   

10.
The theoretical mechanisms for the decays ψ′ → ψπ0 and ψ′ → ψη, which violate SU2 and SU3, respectively discussed. It is argued that symmetry breaking in the decay amplitudes may be as important as π0 −η −η′ mixing. The π0 −η mechanism ψ′ → ψν → ψπ0 leads to Γ(ψ′ → ψπ0) = (3.3±1.0) × 10−3 Γ(ψ′ → ψν), but this number may be enhanced by a factor as large as 12 by π0−η′ mixing and isospin violation in the decay amplitude. The related decays ψ → ηγ and ψ → η′γ are also discussed.  相似文献   

11.
The betaspectra of 12B and 12N have been measured with a NaI crystal as spectrometer. Assuming a shape correction factor 1 + aW + bW2 and b = 1.106 × 10−4 MeV−2, b+ = −1.397 × 10−4 MeV−2, the spectra yield a = (+0.91 ± 0.11) × 10−2 MeV−1 and a+ = (−0.07 ± 0.09) × 10−2 MeV. the aa+ = (+0.98 ± 0.09) × 10−2 MeV−1 is in agreement with the weak magnetism prediction.  相似文献   

12.
Thin films of MnO were deposited by electron beam evaporation using a MnO or MnO2 source. The thin films were charaterized by X-ray and electron diffraction. The Coulomb titration curve reveals a potential plateau of 2.9 V over the composition range 0.05<x<2.0. The chemical diffusion coefficient of lithium in thin films at 15°C is 2.7×10−14 cm2/s for 0<x<0.01 and 2.2×10−15 cm2/s for 0.02<x<0.06. Good reversibility for lithium insertion and extraction is demonstrated by cyclic voltammetry.  相似文献   

13.
O. Pingot 《Nuclear Physics A》1970,150(3):587-592
The βγ circular polarization correlation of the 3 621 keV)3(γ 1692)2+ cascade in 124Sb, the 4+ 662)4+ (γ 796)2+ (γ 605)0+ in 13Z4Cs and the 6+529)6+ (γ 937)4+ (γ 885)2+ (γ 658)0+ in 110mAg have been studied by using a Compton effect polarimeter. The measured asymmetry parameters are 0.172±0.004, −0.0702 ±0.0024 and 0.0549±0.0013 respectively.  相似文献   

14.
The lifetimes of the Cd+ 52P3/2 and 52P1/2 states have been measured by the Hanle effect. The Cd+ ions are produced in a d.c. discharge in cadmium vapor, with helium as buffer gas. The results are: τ(52P3/2) = (2.60±0.20) ×10−9sec, and τ(52P1/2) = (3.05 ± 0.13) × 10−9sec.

We measured also the cross sections for the destruction of the orientation in the 52P1/2Cd+ state (<5Å2), of the orientation (18±10Å2) and of the alignment (46±10Å2) in the 52P3/2 state due to collisions with the helium atoms.  相似文献   


15.
16.
“Rare” annihilation channels for antiprotons stopping on heavy (Ag, Br) nuclei of photoemulsion, have been sought; 4872 stops of antiprotons on photoemulsion nuclei are analysed. Events of formation and decay of the hyperfragment Λ4H, escape of 8He and 8Li nuclei, one-prong stars with the mean range 79.5±5.1 μm of secondary slow “b” particles are found among the annihilation stars at capture on nuclei (Ag, Br). The lower limits for the production probability of Λ4H and 8He, 8Li nuclei per antiproton stopping in the nuclei (Ag, Br) are
WΛ4H2×10−4 and W8He,8Li=(1.3±0.6)×10−3.

The branching ratio for the production of one-prong stars with the secondary “b” particles is at least (1.3±0.6)×10−3. Possible mechanisms for a production of these events in annihilation processes are considered.  相似文献   


17.
A C.W. multi-mode dye laser is used to obtain by optical pumping an orientation of the 2p5 3s3P0 (F = 3/2) state of 21Ne. A magnetic resonance experiment leads to the measurement of the g factor g (3P0) = 3.027 (8) × 10−4 to be compared with the theoretical prediction (3.025(6) × 10−4). One obtains also the metastability exchange cross section σ(3P0) = 18.4 ± 4 Å2 for collisions between metastable (3P0) Ne atoms and ground state Ne atoms. This result is compared with other measurements and theoretical evaluation.  相似文献   

18.
The electronic structure, surface and relaxation energies, and the electric field gradient for the unreconstructed Au(001) surface were calculated by means of the ab-initio all-electron full-potential linearized augmented plane wave slab method. The valence states were calculated within the standard semi-relativistic approach whereas the core states are treated in a fully relativistic way. The Au(001) surface was modelled by free slabs of 5, 7, and 9 layers. From the 9-layer calculation a work function of 5.39 eV was obtained. For the surface energy a value of 1.30 J/m2 for the unrelaxed geometry was derived from the total energies of the 7- and the 9-layer slabs. From total energy minimization of the 7-layer slab, a negative, inward relaxation of −2.6% and a relaxation energy of 14.3 × 10−3 J/m2 were derived. To discuss a mechanism of reconstruction, particular surface states were analyzed in detail in terms of the band structure, layer-dependent density of states and the charge density distribution. Differences of surface and central-layer charge densities show a gain of charge in z-direction localised below and also, to a smaller extent, above the surface atoms. We find a very small gain of delocalised charge in the surface plane between the nearest neighbour positions at the expense of more localised s-d hybridised states. The electric field gradient component Φzz was obtained in a two energy window calculation for which the Au5p states were also treated as band states. The resulting Φzz values are −16.50 × 1017 V/cm2 surface layer, and −3.3 × 1017 V/cm2 for the subsurface layer.  相似文献   

19.
H. Zmora  M. Blau  S. Ofer 《Nuclear Physics A》1969,130(3):541-544
The magnetic moment of the 344 keV level of 152Gd was determined from measurements of the rotations of the angular correlations of γ-γ cascades involving this level in the magnetic hyperfine field of Gd metal. The value found for gτ is (2.43±0.22)·10−11 sec.. Taking τ = (7.6±1.3)·10−11 sec, a value of 0.32±0.06 was derived for the gyromagnetic ratio of this level.  相似文献   

20.
In a study of ∑π+ production by stopped K in liquid helium, (19 ± 6)% of stopped ∑ were observed to decay. This corresponds to a “cascade time” of 28 ± 8 psec.  相似文献   

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