摘要:

Our analysis of two‐quasi‐particle rotational bands in even‐even nuclei reveals an odd‐even staggering in both K+=‖&OHgr;1+&OHgr;2‖ and K−=‖&OHgr;1−&OHgr;2‖ bands. The phase of odd‐even staggering in K+and K−bands is found to be opposite which is in contrast to the behavior of these bands in odd‐odd nuclei. In the present paper, we report the preliminary results of our analysis to understand the behavior of these bands.

ISSN:0094-243X    

DOI:10.1063/1.41163

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Consideration of the ‘‘complete’’ set of expected two‐particle structures in even mass deformed nuclei together with the ‘‘complete’’ set of transitions, connecting states with defined spin and energy ranges and the precisely determined transition energies from crystal spectrometer studies is sought to reveal as yet unidentified levels and band structures involving unplaced transitions. Further a side‐by‐side study of the odd‐odd and the even‐even structures points to a possible isospin dependence of the residual interaction. Energy levels of166Ho and168Er are used to illustrate these features.

ISSN:0094-243X    

DOI:10.1063/1.41164

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The variable moment of inertia model has been applied to the K+=(&OHgr;p+&OHgr;n) bands which are relatively free from Coriolis mixing. The inertia parameter shows significant variation with angular momentum which is nearly identical to one of the odd‐A rotational bands based on either the neutron or the proton configuration also involved in the odd‐odd band. An explanation in terms of the blocking effect of pairing correlations is presented.

ISSN:0094-243X    

DOI:10.1063/1.41165

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.41166

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We consider a system of identical particles distributed in several clusters, each one of which is characterized by a Yamanouchi symbol specifying its permutational symmetry. A procedure for coupling the various clusters into an overall well‐defined angular momentum and permutational symmetry is presented. The results are immediately applicable to the study of nuclear cluster models as well as to nuclei as quark clusters.

ISSN:0094-243X    

DOI:10.1063/1.41167

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Measurements of lifetimes of excited states in nuclei yield crucial information for sensitive tests of nuclear models. Here a novel method will be discussed which involves the GRID (Gamma Ray Induced broadening) technique, in which Doppler broadening is observed in a transition from a nucleus recoiling from the emission of a previous gamma ray. As the recoil energy is extremely small, ultra‐high energy resolving power has to be used. To date all such experiments have been carried out at ILL using the GAMS4 double flat crystal spectrometer which is operated in a NIST ILL collaboration. The method can be used for all lifetimes below a few picoseconds. The wide range of applicability, together with the very exhaustive set of data often obtained, is an advantage with respect to many other methods. The characteristic features of GRID will be discussed using some selected examples.

ISSN:0094-243X    

DOI:10.1063/1.41171

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The theory used to analyze Gamma‐ray Induced Doppler broadening (GRID)is reviewed. The analysis of GRID measurements is done using a collision model which can be used for both monoatomic and polyatomic targets. Very low recoil measurements, as induced by a neutrino (NID), are analyzed using a phonon creation model. Comparison with dedicated experiments is discussed.

ISSN:0094-243X    

DOI:10.1063/1.41172

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Gamma‐ray wavelengths measured with the joint NIST/ILL GAMS4 facility at the High Flux Reactor, Grenoble, France, are discussed. This primary goal of these measurements is gamma‐ray wavelengths which are consistent with the optical wavelength scale and the Rydberg constant with an uncertainty no larger than 0.1 ppm for energies up to 5 MeV. The current status of the Bragg angle and crystal lattice spacing measurements on reference energy values, the neutron mass, and the determination of fundamental constants is reviewed. Measurement of structure factors at high energies is also considered.

ISSN:0094-243X    

DOI:10.1063/1.41173

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We examine proposed mixed symmetry states in both the N=30 and N=84 isotones. In the former case the data are consistent with a mixing of the lowest mixed symmetry state with the two phonon state. This mixing can be described by a perturbation of the strict vibrational limit, due to the introduction of a quadrupole term. This analysis further suggests that no mixing should occur in52Ti, despite the states being separated by less than 200 keV. The case in the N=84 isotones is less clear due to the influence of two neutron excitations which mix and spread the mixed symmetry strength over several states.

ISSN:0094-243X    

DOI:10.1063/1.41174

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Because the inelastic neutron scattering (INS) reaction can be used to populate both collective and non‐collective nuclear states in a statistical manner, it is often possible to probe excited states that cannot be examined with other reactions. Recent advances in Doppler‐shift attenuation method (DSAM) measurements following INS have permitted the determination of lifetimes in the femtosecond regime in heavy nuclei. The measured lifetimes can be used to identify low‐spin collective excitations. Fast E1 transitions have been observed in two different mass regions and, while these transitions can be offered as evidence for octupole‐octupole and quadrupole‐octupole excitations, the occurrence of fast E1 transitions is found to be more common than previously thought. The INS reaction has also been employed to examine the well‐known M1 scissors mode excitations in the rare earth region and 2+mixed‐symmetry states in134Ba.

ISSN:0094-243X    

DOI:10.1063/1.41175

出版商:AIP    

年代:1991

数据来源: AIP