Decay of 0 2 + states in88,92,94Zr andE0 systematics of Zr isotopes

Branching ratios ofE0 andE2 transitions depopulating the 0 ₂ ⁺ states of^{88, 92, 94}Zr have been determined using conversion-electron and γ-ray spectroscopy. Two different lifetime-measurement methods were applied in the remeasurement of the half-lives of the 0 ₂ ⁺ states in^{92, 94}Zr, yielding consistent results ofT _1/2(0 ₂ ⁺ ,⁹²Zr)=85(15) ps andT _1/2(0 ₂ ⁺ ,⁹⁴Zr)=280(40) ps. The monopole strengths extracted areρ ²(⁹²Zr)=8.4(17) ×10^?3 andρ ²(⁹⁴Zr)=11.9(20)×10^?3. The proton configurations of the 0 ₂ ⁺ states are discussed in view of these values and proton transfer data.     

High-spin states in the vibrational nucleus 114 Cd

High-spin states of the neutron-rich vibrational nucleus ¹¹⁴Cd have been studied using the incomplete fusion reaction ¹¹⁰Pd(⁷Li, p2n) and the GASP spectrometer in conjunction with the ISIS Si ball. About 50 new states with excitation energies up to 7 MeV and angular momentum were observed and for many of them, spin and parity could be firmly assigned. The band-like stuctures in ¹¹⁴Cd are compared to the corresponding ones in the even-even neighbour ¹¹²Cd.Received: 31 October 2002, Published online: 17 February 2004PACS: 23.20.Lv transitions and level energies - 27.60. + j      

The 112Cd laboratory: An extension. E0 strengths,multiphonon states and coupled vibrations

The structure of ¹¹²Cd was investigated using the ¹¹¹Cd(n_th,γ) and ¹¹⁰Pd(α,2n) reactions. High resolution crystal and magnetic spectrometers as well as different Compton-suppressed spectrometers were used. The results were combined with published data resulting in a complete level scheme over a large range of spins and excitation energies. The interpretation of the data was performed in the framework of the interacting boson model (IBM). A special effort was put in the interpretation of E0 data and an attempt was made to identify multiphonon and 2₁⁺ ⊗ 3₁⁻ states.     

Decay of 1+ states as a new probe of the structure of 0+ shape isomers

The nuclides 98Mo and 100Mo have been studied in photon-scattering experiments by using bremsstrahlung produced from electron beams with kinetic energies from 3.2 to 3.8 MeV. Six electromagnetic dipole transitions in 98Mo and 19 in 100Mo were observed for the first time in the energy range from 2 to 4 MeV. A specific feature in the two nuclides is the de-excitation of one state with spin J = 1 to the 0+ ground state as well as to the first excited 0+ state, which cannot be explained in standard models. We present a model that allows us to deduce the mixing coefficients for the two 0+ shape-isomeric states from the experimental ratio of the transition strengths from the J = 1 state to the 0+ ground state and to the 0+ excited state.     

Properties of the 2' and 2” states in 106, 112, 114Cd

Angular correlations have been measured between γ-rays from the 2 → 2 → 0 cascades in ^106,112,114Cd and the beam of 11.0 MeV α particles effecting Coulomb excitation. Multipole admixtures for the 2 → 2 transitions, as deduced from these correlations, when combined with earlier results establish their B(E2) and B(M1) values. For the transitions from the 1312 and 1208 keV states in ^112,114Cd the B(E2) values in single-particle units are 18±4 and 24±7. These values are typical for transitions from “two-quadrupole-phonon” states in this mass region whereas that of the 1718 keV transition in ¹⁰⁶Cd has the smaller value of 7.0±2.3. The B(E2) values of the 2 → 2 transitions in ^112,114Cd from the 1468 and 1363 keV states are < 0.3 single-particle units. The B(M1) values of all five transitions are ≈ 10^?2$\text{(}\text{e}\text{h}\text{?}\text{2Mc}\text{)}{}^2$.     

High-spin states in112Cd from the110Pd(α, 2n γ)-reaction

The decay scheme of¹¹²Cd has been studied by γ-ray spectroscopy with the¹¹⁰Pd(α, 2nγ) reaction. Spin and parity assignments were made on the basis of coincidence measurements, angular distributions and excitation functions. Twelve new energy levels were established. A vibrational-like positive-parity band up to spin 8⁺ and a negativeparity side band 5^?, (7^?), (9^?) were found. For the negative-parity states a (v_j, vh_11/2) configuration is suggested. Nuclear Reactions:¹¹⁰Pd(α,2nγ),E _α =15–22.5 MeV; measuredE _γ ,E _γ , (E,E _γ ),E _γ (θ),γ-γ- coincidence;¹¹²Cd deduced levels,J; enriched target.     

Neutrinoless Double-Beta Decay to Excited 0+ States

A considerable effort has been invested in studies of the two-neutrino double-beta decay to the first (and some others, too) excited 0⁺ states. These decay transitions have been considered favourable in terms of the nuclear matrix elements and the possibility to use -coincidence techniques in cleaning the background of the spectrum. A drawback in these studies is the diminished phase space for the emitted leptons due to the smaller Q value of the process. One positive result, namely the decay rate of ¹⁰⁰Mo to the first excited 0⁺ state in ¹⁰⁰Ru, already exists. Encouraged by this result one could argue that a similar situation could prevail also for the neutrinoless double-beta decay to excited 0 ⁺ states. In this article the situation has been studied for several nuclear systems with potential 0 decay to the low-lying 0⁺ states by using the quasiparticle random-phase approximation with realistic nucleon-nucleon interactions.     

Excited 0+ states in 156,158,160,162 Gd

Excited K^π = 0⁺ states in ^{156,158,160,162} Gd isotopes are studied by using the pairing plus quadrupole model (PPQ). To determine the nature and the general trend of the properties of these states depending on the neutron number, B(E2), ρ²(E0) values and two‐nucleon transfer strengths are calculated. We observe that by means of the PPQ model, approximately 13‐14 0⁺ states can be obtained up to 3.3 MeV for the nuclei in question, where most of them are two‐quasiparticle (2qp) in character.     

Low-lying states in112In

Low-lying states below 500 keV excitation in¹¹²In have been investigated via the¹¹²Cd(p, nγ) reaction. New levels have been established atE ^x=206.5keV and 456.1 keV from the measuredγ-ray excitation functions,γ?γ coincidences and the precision measurements of the (p, n) threshold energy of the ground state and of the 206.5 keV state of¹¹²In. Spins and parities of the 206.5 keV state (2⁺) and the 456.1 keV state (3⁺) and multipolarities and mixing ratios of the deexcitationγ-rays have been determined from the angular distributions and linear polarizations of the deexcitation γ-rays as well as the excitation functions of the residual levels. Possible configurations of the newly-found levels are discussed. Half-lives of two states have been remeasured:T _1/2=15.2±0.1 min for the ground state andT _1/2=20.9±0.1 min for the 156.4 keV (4⁺) state. The ground stateQ-value for the¹¹²Cd(p, n)¹¹² In reaction has been measured to be ?3.376±0.006 MeV.     

Cr3+掺杂的Cd3 Al2 Ge3O12光谱特性及晶场参数计算

采用高温固相法合成了Cd3Al2 Ge3O12Cr3 多晶材料,利用X射线衍射对其结构进行了分析,通过Cr3 的室温吸收光谱、室温和77 K发射光谱分别对其光谱特性和晶场参数进行了分析和计算.结果表明:在450 nm的蓝光激发下,Cd3Al2 Ge3O3 室温发射光谱主要由三个宽带及附加其上的弱R线构成,分别对应于C3 的4T1,T2,2T2,4T2到4A2能级跃迁.低温时宽带发射变弱,而R线变得强而锐.Cr3 在Cd3Al2Ge3O12中晶场强度Dq/B为2.32,Stokes位移AE,为1919 cm1,黄昆-里斯因子S为5.58.表明在Cd3Al2Ge3O12中Cr3 处于弱的中等晶场强度,电子-声子耦合较强.4T2零声子能级与2能级的间距△E仅为325.5 cm-1,对Cr3 可调谐激光的输出非常有利.     

Luminescence Spectroscopy and Decay Kinetics of Pr3+ Ions in K3LuSi2O7:Pr3+

Physics of the Solid State - The luminescent characteristics of K3LuSi2O7:Pr3+ (1%), which is a promising optical material for the use as a scintillator, have been studied using a set of...     

关于D0→π－l+νl衰变过程的研究

用光锥QCD求和规则研究D⁰→π^－l⁺ν_l衰变过程, 首先计算D→π跃迁形状因子, 通过构造新的关联函数, 消除了twist-3波函数的不确定性给计算结果所带来的影响, 从而使计算结果更加精确. 计算得到的分支比与最近的实验数据相一致.     

Quadrupole collective properties of 114Cd

The nucleus ¹¹⁴Cd has been Coulomb excited using beams of ¹⁶O, ⁴⁰Ca, ⁵⁸Ni and ²⁰⁸Pb. Several new states have been observed and an almost complete set of reduced E2 matrix elements for the lowest-lying positive-parity states in ¹¹⁴Cd have been measured. In total, about 40 E2 matrix elements have been determined in a model-independent way, including the static quadrupole moments of the 4⁺₁, 6⁺₁, 2⁺₂ and 2⁺₃ states. Large negative static quadrupole moments were found for the 4⁺₁ and 6⁺₁ states and a large positive quadrupole moment for the 2⁺₂ state. All E2 matrix elements involved in the deexcitation of the quintuplet of states at an energy of about 1.2 Me V were determined. The data are compared with predictions by various models, including a configuration mixing calculation within the framework of the IBA model, the harmonic vibrator and a model in which the states of a near-harmonic vibrator are mixed with those of a rotational intruder band with a large deformation. Although no perfect match is obtained, the data favour a vibration-like structure involving levels up to the four-quadrupole phonon multiplet.     

Decay of Cd and levels of Ag

The γ-ray spectrum following the decay of ¹⁰⁴Cd has been investigated with Ge(Li) spectrometers. Two unreported γ-rays with energies of 625.2 and 709.2 keV were observed and placed in the proposed decay scheme.     

Proton-neutron multiplet states in 114In

The γ-ray spectrum of the ¹¹⁴Cd(p, nγ)¹¹⁴In reaction was measured with Ge(Li) and Ge(HP) spectrometers at 4.8, 5.3, and 7.0 MeV bombarding proton energies. The energies (E_γ) and relative intensities (I_γ) of more than 170 γ-ray transitions in ¹¹⁴In have been determined. The electron spectrum of the reaction was measured with a combined magnetic plus Si(Li) spectrometer. Internal conversion coefficients of 38 transitions in ¹¹⁴In were determined for the first time. The level scheme of ¹¹⁴In, γ-ray branching ratios, multipolarity of transitions, level parity and spin values have been deduced. The energies of several ¹¹⁴In proton-neutron multiplets were calculated on the basis of the parabolic rule derived from the cluster-vibration model. The comparison of experimental and theoretical results provided classification of about 18 multiplet states in ¹¹⁴In. The experimental level scheme has also been compared with former theoretical calculations.     

0+ states and E0 and E2 transition rates in even Sn nuclei

0⁺ states and their depopulating E0 and E2 transitions have been studied in ^112–124Sn. Several methods of γ-ray and electron spectrometry have been employed, including special coincidence techniques for lifetime, conversion electron and double Coulomb excitation measurements. For ^114–118Sn the E2 transition probabilities from the first excited 0⁺states (0₂⁺) are about 20 W.u., which is compatible with a vibrational two-phonon character. Also the E0 transition probabilities from these states are within a factor of two from the vibrational values. For the second excited 0⁺ states (0₃⁺) the corresponding E2 and E0 transition probabilities are considerably smaller. A total of 12 E0 transitions have been observed. The 0₃⁺ → 0₂⁺ transition is observed in ^114–120Sn and has in ¹¹⁶Sn a reduced transition probability 1–2 orders of magnitude larger than those of the groundstate E0 transitions, which indicates that the 0₃⁺ and 0₂⁺ states are strong mixtures of components with different 〈r²〉. The 0⁺ states in ¹¹⁶Sn are discussed as possible rotational band heads associated with a deformation β₂ ≈ 0.2. The Coulomb excitation cross section of the 0₂⁺ state is found to be sensitive to an interference term including matrix elements with the 2₂⁺ state. The relative sign of this term has been determined.     

Decay of the mixed states

We study the classical escape from local minima for 2d multi-well Hamiltonian systems, realizing the mixed state. We show that escape from such local minima has a diversity of principally new features, representing an interesting topic for conceptual understanding of chaotic dynamics and applications.