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 531 毫秒
1.
We have performed a theoretical analysis of the ground-state-to-ground-state transitions in 100Mo and 116Cd, based on the quasiparticle random-phase approximation and on a straightforward perturbative scheme. The results show that the single-state dominance found in the realistic calculations of the nuclear matrix elements, which is consistent with data, can be viewed as a result of the interference between few two-quasiparticle configurations. Received: 12 August 2002 / Accepted: 23 October 2002 / Published online: 18 February 2003 RID="a" ID="a"e-mail: civitarese@fisica.unlp.edu.ar Communicated by V.V. Anisovich  相似文献   

2.
The 1/2+ ground state and a 11/2- isomer of very neutron-deficient isotope 143Dy were produced by irradiation of an enriched target of 106Cd with 40Ca and studied by using a helium-jet fast tape-transport system in combination with proton-γ, X-γ and γ-γ coincidence measurements. A simple ( EC + β+) decay scheme of 143mDy with a half-life of 3.0(3) s and a tentative ( EC + β+) decay scheme of 143gDy with a half-life of 5.6(10) s are proposed. As a by-product, the 347- and 545-keV γ transitions in 138Sm following the β-delayed proton emission of 139Gd decay and the 323-keV γ transition in 139Eu following the β-delayed proton emission of 140Tb decay could be observed for the first time. Received: 20 August 2002 / Accepted: 28 October 2002 / Published online: 11 February 2003 RID="a" ID="a"e-mail: xsw@ns.lzb.ac.cn Communicated by D. Schwalm  相似文献   

3.
Combining the Okubo-Zweig-Iizuka rule in the decay φ→ρπ→π+π?π0 with the ρ→4π decay amplitudes, we calculate the φ→2π+?π0 and φ→π+π?0 ones. The partial widths of the above φ decays are evaluated, and the excitation curves in e+e? annihilation are obtained, assuming reasonable particular relations among the parameters characterizing the anomalous terms of the HLS Lagrangian. The evaluated branching ratios Bφ→π+π?0 ≈ 2 × 10?7 and Bφ→2π+?π0 ≈ 7 × 10?7 are such that, with the luminosity L=500 pb?1 attained at DAΦNE φ factory, one may already possess about 1685 events of the decays φ→5π.  相似文献   

4.
From our recent study of properties of the lowest spin-parity 1/2- baryons, N *(1535) and Δ*(1620) , new pictures for the internal structure of the lowest 1/2- baryon nonet and decuplet are proposed. While the lowest 1/2- baryon nonet may have large diquark-diquark-antiquark component, the lowest 1/2- baryon decuplet is proposed to have large vector-meson-baryon components. Evidence for “missing" members of the new pictures is pointed out and suggestions are made for detecting these predicted states from forthcoming experiments.  相似文献   

5.
An accurate calculation of the lowest negative electronic state of H 2 - (fixed nuclei) is reported using the CCSD(T) method and doubly augmented cc-pv5z basis set. Comparison has been made with the reference data by Senekowitsch et al. [Chem. Phys. Lett. 111 (1984) 211]. Owing to larger size of the basisset and inclusion of triple excitations, no vertical shift in this work is necessary to reproduce the asymptotics of H + H -. In addition, the effect of basis-set truncation is estimated, based on the complete-basis-set extrapolation method. The contribution of correlated electron-proton motion to the electron-energy curve for H2 dynamics is pointed out.Dedicated to Prof. Jií Horáek on the occasion of his 60th birthday.  相似文献   

6.
The 19F-13C heteronuclear single quantum coherence (HSQC) experiment is vital for the structural elucidation of polyfluorinated organic species, yet its sensitivity and phaseability are limited by difficulties in uniform excitation of the widely disperse 19F spectral window. Adiabatic pulses of different types have previously been employed to generate effective π pulses for inversion and refocussing, but a systematic comparison of various adiabatic and other inversion pulses has not been published. In this work, it was observed that the use of a broadband inversion pulse (BIP) during the t 1 evolution period resulted in properly phaseable spectra for experiments optimized to detect 1 J CF, in contrast to CHIRP or WURST adiabatic pulses. For the INEPT and reverse-INEPT transfer segments of the HSQC, optimal sensitivity for resonances distant from the transmitter frequency was afforded by optimized universal rotation (BURBOP) or CHIRP pulses. In HSQC experiments with delays optimized for two-bond correlations, only the use of BURBOP pulses in INEPT and reverse-INEPT sequences afforded spectra cleanly phaseable across the F 2 and F 1 spectral windows. This observation is supported by off-resonance pulsed field gradient spin-echo experiments.  相似文献   

7.
The difference in the 332-and 326-keV transition energies from 178Ta decay is measured with a magnetic β spectrometer and a γ spectrometer. The energy of the 332-keV transition (E(332) = 331 607 ± 4 eV) and the energy of the 8 2 ? 1479-keV level in 178Hf (E(1479) = 1479001 ± 6 eV) are determined with high accuracy.  相似文献   

8.
The high-resolution emission spectrum of the A1 Π–X1Σ+ transition of AlH was observed in the 18 000–25 000 cm-1 spectral region using a conventional spectroscopic technique. The AlH molecules were excited in an Al hollow-cathode lamp filled with a mixture of Ne carried gas and a trace amount of NH3. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. In total 163 transition wave numbers belonging to six bands (0-0,1 and 1-0,1,2,3) were precisely measured and rotationally analysed. In the final fit the present data have been combined with available high-resolution measurements of the vibration-rotation bands by White et al. [J. Chem. Phys. 99, 8371 (1993)]. This procedure enabled extracting molecular constants for the A1 Π and X1 Σ+ states of AlH. A very slight local perturbation has been discovered in the v=1 vibration level of the A1 Π state at J=5. This was probably caused by the interaction with the a3Π state.  相似文献   

9.
For the 156Gd and 170Yb nuclei, where the inversion of levels in the Kπ=1? bands is observed, the energies of rotational levels are calculated on the basis of the Coriolis interaction model for the states of two bands whose quantum numbers are Kπ=1?. New 0? levels are introduced in 170Yb, and the structure of 170Er is refined. The interaction parameters calculated for six nuclei are considered within the structure predicted by the quasiparticle-phonon model.  相似文献   

10.
The cross sections for rotational, fine-structure and projection-change transitions in collision of MgH (2Σ+) molecule with 3He and 4He atoms were computed at cold and ultracold temperatures using the ab initio potential energy surface. The significant suppression feature and resonance pattern caused by spin-rotation interaction were found and discussed. The collisions exhibit a strong isotope effect in the ultracold regime. The rotational relaxations of the fine-structure excited energy levels tendentiously preserve the F index. The ratio of the cross sections for elastic and spin-flipping collision with 3He partner is always greater than seven orders of magnitude for the energy range 10-6−1cm-1 and suggests the MgH molecule is a good candidate for 3He buffer gas cooling.  相似文献   

11.
We propose a method for EIT ground state cooling of 171Yb+ ion, which involves three light fields with detuning on a MHz scale. The steady-state mean vibrational quantum number is calculated to be less than 0.005. Efficient cooling is achievable in a motional-mode frequency range of 2π · (1.5 ± 0.5 MHz).  相似文献   

12.
In this article, we calculate the vector form factors f+ (Q2) and f- (Q2) within the framework of the light-cone QCD sum rule approach. The numerical values of f+ (Q2) are compatible with existing theoretical calculations, and the central value of f+ (0) (f+ (0)=0.97) is in excellent agreement with the values from chiral perturbation theory and lattice QCD. The values of |f- (0)| are very large compared to the theoretical calculations and experimental data, and they cannot give any reliable prediction. At large momentum transfer with Q2 > 5 GeV2, the form factors f+ (Q2) and |f- (Q2)| can either show the asymptotic behavior of or decrease more quickly than ; more experimental data are needed to select the ideal sum rules. PACS 12.38.Lg; 12.38.Bx; 12.15.Hh  相似文献   

13.
14.
The relative method was used to measure the photofission cross sections for 243Cm and 249Cf isotopes in the energy range from 6 to 12 MeV, for 245Cm in the energy range from 5 to 10 MeV, and for 249Bk in the energy range from 5.5 to 10 MeV. The measurements were performed with an energy step of 50 to 200 keV by using the microtron installed at the Institute of Physics and Power Engineering (Obninsk). The cross section for 238U photofission was used as a reference in these measurements. Data on the cross sections for 243Cm, 245Cm, and 249Bk photofission were obtained for the first time, while data on the cross section for 249Cf photofission were obtained for the first time only in the energyregion E<10 MeV. The data on the 245Cm nucleus suggest that, in the energy region around 6 MeV, the cross section for its photofission has a maximum, which is likely to be due to the low-energy resonance structure of the dipole-photoabsorption cross section. For 249Cf, an anomalously large value of the photo fission cross section is observed in the region of the first maximum of the giant dipole resonance (E≈11 MeV). By comparing the energy dependences obtained for the fissilities of the 243Cm and 249Bk isotopes from photofission data with the fissilities from direct-reaction data, it is found that the observed fission thresholds agree and that there is a plateau-like dependence at energies above 7.5 MeV. For the 245Cm and 249Cf nuclei, there are no similar data for performing such a comparison. Data on the fissilities as obtained from the present series of relative measurements that employ the microtron bremsstrahlung spectrum are analyzed.  相似文献   

15.
A new method of analysis of resonant parameters in the framework of the J-matrix inverse scattering formalism is proposed. The method is applied to analysis of scattering in various partial waves. The obtained 1/2? and 3/2? resonance energies and widths in 5He and 5Li nuclei are in good agreement with the results of other approaches. The eigenenergies entering the J-matrix phase shift parameterization are shown to correlate well with the respective results of no-core shell model calculations, in particular, in the case of non-resonant s-wave scattering.  相似文献   

16.
The reaction of π0π+ photoproduction on free and quasi-free protons with γ-ray energies from 0.5 to 1.5 GeV has been studied. Its cross section was measured in the range θ π 0 ≥ 20°. The distributions of π0π+, π0n, and π+n invariant masses were analyzed. The experiment was performed using the Compton back-scattered γ-ray beam at the GRAAL facility (Grenoble, France), applying liquid deuterium and hydrogen targets and a large-aperture (almost 4π) detector. Particular attention was paid to analysis of systematic errors related to the neutron detection efficiency.  相似文献   

17.
The two-neutrino positron double-beta decay of 106Cd for the 0 + 0+ transition has been studied in the Hartree-Fock-Bogoliubov model in conjunction with the summation method. In the first step, the reliability of the intrinsic wave functions of 106Cd and 106Pd nuclei has been tested by comparing the theoretically calculated results for yrast spectra, reduced B(E2: 0+ 2+) transition probabilities, quadrupole moments Q(2+) and gyromagnetic factors g(2+) with the available experimental data. In the second step, the nuclear transition matrix element M2 and the half-life T1/22 for the 0 + 0+ transition have been calculated with these wave functions. Moreover, we have studied the effect of deformation on the nuclear transition matrix element M2.  相似文献   

18.
Cross-sections, beam asymmetries, and recoil polarisations for the reactions γpK +Λ;γpK +Σ0, and γpK 0Σ+ have been measured by the SAPHIR, CLAS, and LEPS Collaborations with high statistics and good angular coverage for centre-of-mass energies between 1.6 and 2.3 GeV. The combined analysis of these data with data from π and η photoproduction reveals evidence for new baryon resonances in this energy region. A new P11 state with mass 1840 MeV and width 140 MeV was observed contributing to most of the fitted reactions. The data demand the presence of two D13 states at 1875 and, optimistically, at 2170 MeV.  相似文献   

19.
We present a first detailed experimental study of the C(3)1Σ+ state of the NaRb molecule converging to the Na(3p) + Rb(5s) states of separated atoms. Two different high resolution spectroscopic methods have been applied: the Fourier transform spectroscopy of laser induced fluorescence and the V-type optical-optical double resonance polarization labeling spectroscopy. The entire data field for the C1Σ+ state of Na85Rb and Na87Rb consists of rovibrational levels with v'=0–64 and J'=4–123. The data were incorporated into a direct fit of a single potential energy curve to the level energies using the Inverted Perturbation Approach method. As the experimental data extend to the “shelf" region of the potential at large internuclear separations of 8.5 ?, the C state's suitability for photoassociation yielding cold heteronuclear NaRb is discussed. Electronic supplementary material Online Material  相似文献   

20.
The scheme of the β-decay of 234Th is still not completely clear. Only the upper bound (10 keV) of the energy of the isomeric transition from level T1/2 = 1.17 min of the 234Pa nucleus is known, and the correspondence between gamma quanta of several energies emitted in the β-decay of 234Th and specific nuclear levels of 234Pa has not been established. In this work, the isomeric transition energy of 2.6 ± 0.5 keV is determined via the γ-spectrometry of a 234Th source in γγ-coincidences, and a new 234Pa level populated in the β-decay of 234Th is introduced.  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