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1.
The 20Ne(p, γ)21Na capture reaction has been studied in the energy range Ep = 0.37–2.10 MeV. Direct-capture transitions to the 332 (52+) and 2425 keV (12+) states have been found with spectroscopic factors of C2S(1d) = 0.77±0.13 and C2S(2s) = 0.90±0.12, respectively. The high-energy tail of the 2425 keV state, bound by 7 keV against proton decay, has also been observed in the above energy range as a subthreshold resonance. The excitation function for this tail is consistent with a single-level Breit-Wigner shape for a γ-width of Γγ = 0.31±0.07 eV at Ex = 2425 keV. The extrapolation of these data to stellar energies gives an astrophysical S-factor of S(0) = 3500 keV · b. Two new resonances at Ep = 384±5 and 417± 5 keV have been observed with strengths of ωγ = 0.11±0.02 and 0.06±0.01 meV, corresponding to the known states at Ex(Jπ) = 2798 (12?) and 2829 keV (presumably 92+), respectively. For the known Ep = 1830 keV resonance, a strength of ωγ = 1.0± 0.3 eV and a total width of Γ = 180± 15 keV were found. Branching ratios as well as transition strengths have been obtained for these three states. The Q-value for the 20Ne(p, γ)21Na reaction (Q = 2432.3 ± 0.5 keV) as well as excitation energies for many low-lying states in 21Na have been measured. No evidence was found for the existence of the state reported at Ex = 4308±4 keV.In the case of 22Ne(p, γ)23Na, direct-capture transitions to six final bound states have been observed revealing sizeable spectroscopic factors for these states. The astrophysical S-factor extrapolated from these data to stellar energies, is S(0) = 67 ± 12 keV · b.The astrophysical as well as the nuclear structure aspects of the present results are discussed.  相似文献   

2.
Neutron capture and transmission measurements have been carried out on the separated isotopes of 147Sm (98.34 %) and 149Sm (97.72 %) at the 55 m time-of-flight station of the Japan Atomic Energy Research Institute electron linear accelerator. Resonance energies and neutron widths for a large number of resolved resonances were determined up to 2 keV for 147Sm and 520 eV for 149Sm. Radiation widths for 5 resonances in 147Sm + n and 7 resonances in 149Sm + n were derived. The s-wave strength functions, average level spacings and average radiation widths were obtained to be: 104S0 = 4.8 ± 0.5, D = 5.7 ± 0.5 eV and Γγ = 69 ± 2 meV for147Sm; a 104S0 = 4.6 ± 0.6, D = 2.2 ± 0.2 eV and Γγ = 62 ± 2 meV for149Sm. The average capture cr sections were deduced from 3.3 to 300 keV with an estimated accuracy of 5 to 15 %. The measured capture cross sections for 149Sm are largely different from the evaluated data, which are obtained based on the statistical model calculation. Possible reasons for this disagreement are discussed.  相似文献   

3.
From the angular distributions of γ-rays emitted by oriented 129gTe and 129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of 129I at 487.4 keV (52+), 696.0 keV (112+), 729.6 keV (92+), 768.9 keV (72+), 1050.4 keV (72+) and 1111.8 keV (52+). In addition, E2/M1 amplitude ratios for the following 129I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076+0.037?0.148); δ(487.4) = 0.50+0.17?0.10 or δ? = 0.35+0.15?0.09; δ(556.7) = 0.06±0.02 or δ? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ?1 =0.20±0.03 if Iπ (845 keV) = 72+; δ(1022.6) = ?(0.02 ±0.02) or δ?1 = ?(0.23±0.02); δ(1084) = 0.56 +0.04?0.14; δ(1111.8) = 0.06±0.05 or δ?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes 12+ as a possible spin assignment for the 559.6 keV level, so that no 12+ level is fed in the decay from 129Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model.  相似文献   

4.
Primary capture γ-rays have been studied for 38 177Hf neutron resonances with energies in the range 1–165 eV. Intensities were measured for 29 transitions ending at states with an excitation energy in 178Hf up to 2050 keV. The analysis was facilitated by the previous knowledge of the spin and parity of all neutron resonances and of most low-lying states. For nine final levels, which had not previously been seen, information on J and π was deduced from the corresponding average intensities. The distribution of partial widths was fitted with a χ2 function with ν = 1.38?0.13+0.18 degrees of freedom for E1 radiation and ν = 1.5?0.40+0.60 for M1 radiation. The average El reduced photon strength was found to be SEl = 〈Γγitij/DEγ5〉A?83 = (4.8 ± 1.0) × 10 ?15MeV?5 and the ratio between El and Ml intensities equal to 5.5 ± 1.4. A comparison of this value for the El strength with those reported for other nuclei with A$?= 100 showed that the intensities follow the A-dependence predicted by the Brink-Axel model. A non-statistical effect was observed, consisting of an enhancement of El transition probalilities to K = 2, 3 final states as compared to K = 0, 4 states.  相似文献   

5.
We report the first observation of the decay ?′→?π+π?l+l?π+π?. The 7 events seen yield a branching ratio B(?′→+π?)=(19±8)%. A consistent value of B=(26±13)% is obtained from the charged multiplicities of the ?′ and ? decays. Using these values we deduce Γtot(?′)=(31+10?8) keV and Bee(?′)=(1.8±0.5)%. Furthermore we estimate Γ(?′→gg?)=(10±5) keV in agreement with QCD predictions using vector gluons while one would expect 100 keV with scalar gluons.  相似文献   

6.
The high-energy tail of the Jπ = 12+, 2425 keV state in 21Na, bound by 7 keV against proton decay, has been observed in the 20Ne (p,γ)21Na reaction at Ep=0.5?1.5 MeV. The observed excitation function is consistent with a single-level Breit-Wigner shape with Γγ=0.31±0.07 eV at Ex = 2425 keV.  相似文献   

7.
The λφ24 Euclidean (quantum) field theory is studied in the multiphase region, and the following results are proven: (1) The “low temperature” expansion converges for Dirichlet (D), free (F), Neumann (N), and periodic (P), boundary conditions, and the even-point Schwinger functions for these boundary conditions have a mass gap; (2) ob = 12〈o〉+ + 12 〈o〉?, where b = D, F, N, P, and 〈o〉± are the pure states of Glimm, Jaffe, and Spencer; (3) 〈o〉±ξ = 〈o〉± for all ξ > 0, where ξ is the buondary field; (4) alternative characterizations of the pure states 〈·〉± are given.  相似文献   

8.
A fluctuation analysis technique and the comparison of experimentally deduced strength distributions with a statistical one have been used to extract level densities as a function of excitation energy from high-resolution inelastic electron scattering spectra. Both methods yield for the Jπ = 2? states around Ex = 9 MeV in 90Zr mean level spacings 〈D〉 = 6.5±1.6 keV and 〈D〉 = 5.5 ± 1.5 keV, respectively. Those level densities are then employed to estimate the magnetic quadrupole strength that is hidden in the background and escaped direct experimental detection.  相似文献   

9.
We present a microscopically-founded potential model for the 13N(p, γ)14O reaction at energies of astrophysical interest. The model is shown to reproduce the 13C(p, γ)14Ocross section very well. The 13N(p, γ)14O reaction is dominated by the first excited J = 1? resonance in 14O. For this resonance we find a proton width of Γc.m. = 40.1 keV and a photon width of Γγ = 1.50 eV.  相似文献   

10.
It is well known that the observation of a nonzero Fermi matrix element for a β-transition between states that differ in isospin can provide information about the relative isospin purity of the states involved. We have determined the log ft value for the 0+ → 0+ (ΔT ≠ 0) β-transition in 64Ga64Zn decay as 6.516 ± 0.020. From this log ft value, we have deduced |MF| = (43.4 ± 1.1) × 10?3, |α| = (21.7 ± 0.6) × 10?3 and |〈VCD〉| = 41.7 ± 1.1 keV, where MF2 and 〈VCD〉 represent the Fermi matrix element, isospin impurity and Coulomb matrix element, respectively. The Coulomb matrix element of 41.7 keV found for 64Ga is one of the largest known from β-decay experiments. The experimental procedure involved a careful measurement of the intensity of the annihilation radiation relative to that of the other γ-rays from 64Ga decay. As a by-product, we have obtained an improved 64Ga decay scheme. We have also summarized the existing information on the isospin impurities of nuclear states as deduced from β-decay experiments.  相似文献   

11.
The γ-decay of 26 resonances in the reaction 60Ni(p, γ)61Cu in the range Ep = 3690–3790 keV has been investigated. The g92 isobaric analogue state (IAS) corresponding to the parent state at E1 = 2114 keV in 61Mi has been resolved into several fine structure components. The absolute strength for the transition to the antianalogue state is found to be Γγ = 0.24 ± 0.07 W.u. The measured M1 strength distribution for the decay of the g92. IAS is compared to theoretical predictions.  相似文献   

12.
The half-life of the 238U shape isomer and its yield ratio in a (γ, γ') reaction have been measured by pulsed beam techniques at a bremsstrahlung endpoint energy of 12 MeV. From the results (T12 = 146 ± 22 ns, Yiso/Ypr = (6.6 ± 1.0) × 10?6) the isomeric fission cross section has been deduced. Combining this information with the results of a previous 238U(γ, xnγ) study, an upper limit for the branching ratio Γγ/Γf|II < 13 for the decay of 238mU can be obtained. The decay properties of the 236U and 238U shape isomers are discussed.  相似文献   

13.
The decay K+ → e+υγ has been investigated. For the structure-dependent part with positive γ-helicity (SD+) the branching ratio Γ(SD+)Γ(Kμ2) = (2.33 ± 0.42) × 10?5 is obtained from 51 ± 3 events observed in the kinematical region Ee ? 235 MeV, Eγ > 48 MeV and θeγ > 140°. For the corresponding part with negative γ-helicity we obtain an upper limit Γ(SD?)/Γ(SD+) < 11 (90% CL) from the sample of electrons with energies 220 MeV ? Ee < 230 MeV and with no γ in the backward direction. This upper limit implies that the ratio of structure-dependent axial vector amplitudes lies outside the region ?1.8 < aKυK < ?0.54.For the decay K+e+ννν the limit Γ(K+e+ννν)/Γ(Ke2) < 3.8 90% confidence level) was found.  相似文献   

14.
A high-accuracy investigation of the level scheme of 47V has been performed using the 46Ti(p, γ)47V reaction. The γ-decay schemes of the strong (p, γ) resonances at Ep = 1546, 1549, 1565 and 1572 keV lead to 17 new energy levels in 47V with excitation energies between 2.7 and 5.1 MeV. From the (p,γ) angular distributions mixing ratios of the primary γ-transitions and Jπ values of the resonances and of many states populated in the γ-decay have been determined. The total width of the Ep = 1549, 1565 and 1572 keV resonances for γ-decay are found to be Γγ = 0.12, 0.15 and 0.03 eV, respectively. The Q-value of the 46Ti(p,γ)47V reaction is found to be 5168.6 keV. The two resonances at Ep = 1549 and 1565 keV, which have Jπ = 32?, are interpreted as fine structure components of the analogue state of the E1 = 2.545 MeV Jπ = 32? level in 47Ti while the (72) resonance at Ep = 1546 keV might correspond to the E1 = 2.615 MeV72? parent state in 47Ti. The analogue-antianalogue M1 transition strength of the split 32? analogue state is 0.01 single-particle units and fits well into our systematics of IAS → AIAS transitions in fp-shell nuclei.  相似文献   

15.
The difference of the cross sections for deep inelastic scattering of muons with average momenta 21 GeV/c with right and left helicity at large angles, i.e., with large momentum transfer, has been measured. No statistically-significant dependence of cross sections on the longitudinal polarization of muons has been found, i.e. no parity-nonconservation effects in deep inelastic μN interaction have been observed. The magnitude of the cross-section asymmetry R = [〈σR〉 ? 〈σL〉][〈σR〉+ + 〈σL〉] may be represented as R = βQ2〉 = (? 4 ± 6) × 10?3Q2, (GeV/c)2〉. The limitations Go(μ) = (+ 6 ± 10)G have been obtained for the constant Go(μ) of vector-axial interaction (Go(μ)2) [μγα(1 + γ5)μ] Jαo (hadron, V-A).  相似文献   

16.
Energy levels of 85Rb and 87Rb have been studied via de-excitation γ-rays following Coulomb excitation with 35Cl ions. In addition to the known negative-parity states at 151.2 keV and 868.2 keV in 85Rb, two states at 281.0 keV and 731.8 keV have been found with fourγ-ray transitions of 129.8, 281.0, 450.8 and 731.8 keV. Only one Coulomb excited state at 402.6 keV in 87Rb has been observed. The B(E2↑) values (in units e2 · b2) have been determined as 0.0035±0.0004 (151.2 keV), 0.0016±0.0002 (281.0 keV), 0.0101 ±0.0010 (731.8 keV), and 0.036±0.004 (868.2 keV) for the states in 85Rb, and as 0.0054±0.0006 (402.6 keV) for the state in 87Rb. The mean lifetimes of the 731.8 keV and 868.2 keV states have been measured by the Doppler shift attenuation method as 6.4±0.7 psec and 4.2±0.5 psec respectively. Angular distribution measurements allow unique spin and parity assignments of 12? and 32? to the 281.0 keV and 731.8 keV levels respectively. The spin and parity of the 868.2 keV level has been restricted to 52? or 72?.  相似文献   

17.
From the measurement of Be+e? = Γ(ppe+e?)Γpp→total = (3.2 ± 10?7), obtained in an experiment at CERN with antiprotons at rest, a value of the proton electromagnetic form factors at the threshold of the time-like region is derived: |GE| = |GM| = 0.51 ± 0.08 at q2 = -3.52 (GeV/c)2.  相似文献   

18.
Reflectance spectra were measured on ZnTe in magnetic fields up to 18 T for B ? [100] and B ? [110]. The experiments yield renormalized valence band parameters γ12 = 0.83 ± 0.08 and γ13 = 1.30 ± 0.12, corresponding to bare parameters γ2 = 0.95 ± 0.09 and γ3 = 1.48 ± 0.14. From the free exciton Rydberg energy R10 = 12.8 meV we derive a reduced exciton polaron mass m0 0.080 ± 0.005 and a bare reduced mass m0 0.074 ± 0.005, corresponding to γ11 = 3.9 ± 0.7 and γ1 = 4.4 ± 0.7 for an electron effective polaron mass m1e = 0.116 m0. We further calculate the exciton diamagnetic shift rate according to existing low-field theories modified by a variational calculation taking into account polaron effects and valid up to γ ? 1. The difference between experiment and theory is 10% and the agreement is considered satisfactory.  相似文献   

19.
20.
Measurements have been made of some parameters of the second and sixth T = 32 states in 17F. For the second state, the resonance energy was found to be Ep = 12.707 ± 0.001 MeV (En = 12.550±0.001 MeV), which agrees with and improves on the accuracy of earlier work. For the sixth T = 32 state, at Ep = 14.435 MeV, the γ-decay was determined to be predominantly γ0 with a branch to the first excited state of Γ(γ1)/Γ(γ0) ≦ 0.14. Together with other work, this determines Jπ to be 32?. The capture strength is found to be (2J + 1)ΓpΓγ/Γ = 11.4 ± 2.6 eV.  相似文献   

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