Description of the properties of the low-lying energy states in 100Mo with IBM2

The properties of the low-lying energy states for the 100Mo isotope is investigated within the framework of the proton-neutron interacting model IBM2.By considering the relative energy of the d proton boson to be diferent from that of the neutron boson and taking into account the dipole interacting among like-boson LπLπand LνLν,the low-lying energy spectrum is reproduced well.Particularly,the relative position of the energies for 2+1,0+2,2+2 and 4+1states shifted correctly fit the experimental data.The electromagnetic properties,including the key observable B(E2)reduced transition branching ratios and the E2 reduced matrix elements of the experimental data,are well described.Our calculations show possible shape coexistence in the 100Mo nucleus.     

Structure of the low-lying states of 47Ti

Deformed configuration-mixing calculations for the nucleus ⁴⁷Ti have been performed in the framework of the projected Hartree-Fock formalism. For each of the angular momentum states, the Hamiltonian has been diagonalized in the basis of about ten of the lowest orthogonalized projected states. The resulting spectrum is in good agreement with the observed spectrum of negative parity states. The eigenstates of the Hamiltonian have been analysed for the possible existence of the “band structure”. Besides the “ground state” $\text{K =}\text{5}\text{2}$ band of states with deformation δ ≈ 0.15, another well defined band of states belonging to the $\text{K =}\text{1}\text{2}$ neutron excited intrinsic state is likely to exist. The calculated and experimental binding energies are in good agreement. The results of the detailed calculation have been extrapolated to obtain an estimate of the level density for ⁴⁷Ti up to 6 MeV excitation energy.     

Quasi-relativistic treatment of the low-lying KCs states

The potential energy curves, permanent and transition dipole moments as well as spin-orbit and angular coupling matrix elements between the KCs electronic states converging to the lowest three dissociation limits were evaluated in the basis of the spin-averaged wavefunctions corresponding to pure Hund’s coupling case (a). The quasi-relativistic matrix elements have been obtained for a wide range of internuclear distance by using of small (9-electrons) effective core pseudopotentials of both atoms. The core-valence correlation has been accounted for a large scale multi-reference configuration interaction method combined with semi-empirical core polarization potentials. The static dipole polarizabilities of the ground X¹Σ⁺ and a³Σ⁺ states were extracted from the closed-shell coupled-cluster energies by the finite-field method. Among the singlet and triplet Σ⁺ states manifold the pronounced avoided crossing effect between repulsive walls of the (2,3)³Σ⁺ states has been discovered and analyzed by finite-difference calculation of radial coupling matrix elements. The resulting transition dipole moments and potentials were used to predict radiative lifetimes and emission branching ratios of excited vibronic states while the calculated angular coupling matrix elements were transformed to Λ-doubling constants of the (1,2)¹Π states and magnetic g-factor of the ground state. The accuracies of the present results are discussed by comparing with experimental data and preceding calculations.     

Isomerism of low-lying states in 86Y

Low-energy isomeric states of ⁸⁶Y were populated in the reaction ⁷³Ge + ¹⁶O at 57MeV and were investigated by means of delayed n $ \gamma$ and $ \gamma$ $ \gamma$ coincidences. A half-life of 70(7)ns was measured for the 5^- state at 208keV, yielding an exceptionally small B(M1) value of 2.0(7)×10^-5 W.u. and a B(E2) value of 0.34(⁺²⁴ _-13) W.u. For the other three known isomeric states at 218, 243, and 302keV, the half-lives extracted from the present experimental data are in very good agreement with previous measurements. Given the newly observed isomeric character of the 5^- 208keV state, the re-analysis of earlier experimental data on the 302keV isomer led to a new spin-parity assignment, 6⁺, for this state. In addition, this re-evaluation provided two g -factors, -0.083(3) and +0.63(2) , for the 208 and 302keV states, respectively. The results are discussed in terms of spherical-shell model calculations performed with a truncated space of configurations built on the f _5/2 , p _3/2 , p _1/2 , and g _9/2 valence orbitals. Effective spin, orbital, and “tensor” g -factors were determined empirically for protons and neutrons in the considered configuration space.     

Influence of one-particle states in the continuum on the low-lying, negative-parity states in O

Balashov's resonance approximation is used to calculate the level shifts and widths of the low-lying, negative-parity states in ¹⁷O, assuming these states to be 2p-1h structure. It turns out that the coupling to one-particle continuum states is very important not only for the widths but also for the positions of most of the levels. The results prove to be very sensitive to the positions of the single-particle resonances in the (2p, 1f) shell.     

101Mo衰变的研究

采用γ－γ－ｔ三参数快慢符合谱仪研究了＾１０１Ｍｏ→β＾－＾１０１Ｔｃ的衰变,利用符合测量结果构造了一个新的＾１０１Ｍｏ→β＾－＾１０１Ｔｃ的衰变纲图,首次确定了１０４．７０,１０５．９５,７７４．１５ｋｅＶγ射线的位置,首次观测到１５０８．０１ｋｅＶ的γ射线并确认了其跃迁位置。     

Properties of the low-lying positive-parity states in Be and C

Excitation energies and electromagnetic form factors of the low-lying positive-parity states have been calculated in⁹Be and ¹³C on the basis of a particle-core coupling model. The results are compared with recent electron scattering experiments and photon data. The first excited levels in the two nuclei show a large contribution from the spin term of the electromagnetic interaction at low-momentum transfer q² < 0.6 fm⁻².     

Description of the low-lying negative parity states in153Gd

To explain the properties of the recently observed negative parity states in the 89-neutron nucleus¹⁵³Gd, the Nilsson model is extended to include the Coriolis couplings between the 3^?/2 [521], 5^?/2 [523], 3^?/2 [532], 1^?/2 [530], 1^?/2 [510], 1^?/2 [521] and 5^?/2 [512] bands. The calculation reproduces rather well the experimental level energies, single neutron transfer cross sections and electromagnetic transition rates.     

Triplet exciton states in ammonium tetraphenylborate crystals

In the study of spontaneous exciting luminescence of polycrystalline BPh₄NH₄ structures, it was shown that observed luminescence is caused by triplet exciton states which are stable at low temperatures under dark conditions. Triplet excitons are formed when an electron is transferred from the anionic part of complexes to cations of neighboring complexes. The ATPB crystal structure makes it possible to switch ∼2% of complexes from states with S = 0 to the state with S = 1, i.e., to provide high density of data recording. Information is read when luminescence is excited and is erased when a structure is heated to room temperatures. Switching of ATPB states from S = 0 to S = 1 by light should be of interest for spintronics.     

NaCCH自由基低能电子态的理论研究

采用CASSCF/CASPT2方法研究了NaCCH自由基的低能电子态,在C2v对称性下给出了NaCCH自由基9个低能激发态的几何、组态、CI系数、振子强度、垂直激发能和绝热激发能.研究结果表明,NaCCH自由基的基态X1Σ+几何和转动系数与实验值是一致的;谐振频率与其他理论方法得到的值也符合的很好;HOMO和LUMO轨道的能量间隔为3.80eV,对应着13Σ+的绝热激发能;除13Π外,其它低能激发态均是稳定状态;基态到三重态是自旋禁阻的.     

Shape mixing dynamics in the low-lying states of proton-rich Kr isotopes

We study the oblate–prolate shape mixing in the low-lying states of proton-rich Kr isotopes using the five-dimensional quadrupole collective Hamiltonian. The collective Hamiltonian is derived microscopically by means of the CHFB (constrained Hartree–Fock–Bogoliubov) + Local QRPA (quasiparticle random phase approximation) method, which we have developed recently on the basis of the adiabatic self-consistent collective coordinate method. The results of the numerical calculation show the importance of large-amplitude collective vibrations in the triaxial shape degree of freedom and rotational effects on the oblate–prolate shape mixing dynamics in the low-lying states of these isotopes.     

The low-lying states and configurations in138La

Tritons from the reaction¹³⁹La(d, t)¹³⁸La atE _d=16 MeV were analyzed at eleven reaction angles from 22 ° to 90 ° with a broad-range magnetic spectrograph. TheQ-value of the reaction is ?2522±5 keV. The nine lowest-lying states in¹³⁸La are interpreted in terms of the shell model configurations (πg _7/2)^?1 (vd _3/2)^?1, (πg _7/2)^?1 (vs _1/2)^?1 and (πg _7/2)^?2 (πd _5/2)^?1(vd _3/2)^?1. Seven levels in the energy range of 700–1300 keV are populated byl=5 transitions and are interpreted as coming from the (πg _7/2)^?1(vh _11/2)^?1 configuration. The ground state of¹³⁸La is shown to haveJ ^π=5⁺. Therefore, beta decay by unique second-forbidden transitions to the 2⁺ one-phonon states of¹³⁸Ce and¹³⁸Ba must be inferred in spite of unusually high logft values of 19.2 and 18.5, respectively.     

Molecular opacities of low-lying states of oxygen molecule

The X~3∑_g~-,A'~3△_u,A~3∑_u~+,1~3Π_g,and B~3∑_u~-electronic states of oxygen molecule(O_2) are calculated by the multiconfiguration self-consisted filed(MRCI)+Q method with the scalar relativistic correction and core-valence correlation correction.The obtained spectroscopic constants of the low-lying bound states are in excellent agreement with measurements.Based on the accurately calculated structure parameters,the opacities of the oxygen molecule at the temperatures of 1000 K,2000 K,2500 K,and 5000 K under a pressure of 100 atm(1 atm=1.01325×10~5 Pa) and the partition functions between 10 K and 104 K are obtained.It is found that with the increase of temperature,the opacities for transitions in a long wavelength range are enlarged because of the larger population on excited electronic states at the higher temperatures.     

A calculation of low-lying collective states in even-even nuclei

We present results of a calculation of the low-lying collective quadrupole states in even-even nuclei within the framework of the proton-neutron interacting boson model.     

Structure of excited states in100Mo and102Mo from spectroscopy using18O induced reactions

The lifetimes have been determined for the 2⁺, 0^+～ and 4⁺ states in¹⁰⁰Mo and¹⁰²Mo using the recoil-distance Doppler-shift method. The states have been excited in¹⁰⁰Mo by Coulomb excitation and in¹⁰²Mo by the two-neutron transfer reaction induced by¹⁸O ions on a¹⁰⁰Mo target. The study of the excitation function for the elastic and inelastic scattering on the ground and first excited 2⁺ state in¹⁰⁰Mo at beam energies between 20 and 61 MeV shows that 40 MeV is the highest incident energy for pure Coulomb excitation. Above this energy nuclear absorption sets in and nuclear scattering contributes to the excitation of the 2⁺ state of¹⁰⁰Mo. From the lifetimes of the 2⁺ and 4⁺ states deformation parameters of ¦β¦= 0.21 and ¦β¦=0.31 for¹⁰⁰Mo and¹⁰²Mo respectively were deduced. The 0^+′ levels are not shape isomeric states, as suggested earlier, but they decay by enhancedE2 transitions to the first 2⁺ states. From a comparison with similar states in other transitional nuclei it is suggested that they are band heads forβ vibrational bands.     

Gamma decay of low-lying states in S and Ar

Decay modes and lifetimes of low-lying levels in ³⁰S and ³⁴Ar were investigated by the Doppler-shift attenuation method using the ²⁸Si(³He, n)³⁰S and ³²S(³He, n)³⁴Ar reactions. The lifetimes measured in ³⁰S were (in fs): τ_m(2210) = 310 ± 75, τ_m(3402) = 160 ± 45 and τ_m(3664) > 1400; and in ³⁴Ar: τ_m(2090) = 150 ± 50, τ_m(3286) = 120 ± 65 and τ_m(4513) = 300 ± 80, also in fs. These results are compared with theoretical calculations. A comparison of the E2 decay strengths in masses 30 and 34 is also made to test the isospin dependence of electro-magnetic transitions.