Two-phonon Γ-vibrational Band Research Articles

Possible very anharmonic one- and two-phonon γ-vibrational bands in 103Mo

High-spin levels of [Formula: see text]Mo have been reinvestigated by analyzing the high statistics [Formula: see text]-[Formula: see text]-[Formula: see text] and [Formula: see text]-[Formula: see text]-[Formula: see text]-[Formula: see text] coincidence data from the spontaneous fission of [Formula: see text]Cf taken with the Gammasphere detector array. Two bands and 30 new transitions have been identified. A potential energy surface calculation has been performed. The calculation confirmed the 3/2[Formula: see text][411] configuration of the ground state band and 5/2[Formula: see text][532] for the 346[Formula: see text]keV excited band, as assigned in the previous work. The two newly established bands were proposed to be one- and two-phonon [Formula: see text] vibrational bands coupling to the 5/2[Formula: see text][532] Nilsson orbital, respectively. Triaxial projected shell model calculations have been applied to explain the level structure and are found in good agreement with experimental data.

Reinvestigation of two-phonon γ-vibrational band in neutron-rich 114Pd

The level structure in neutron-rich [Formula: see text]Pd nucleus has been reinvestigated by measuring prompt [Formula: see text] rays emitted in the spontaneous fission of [Formula: see text]Cf. A two-phonon [Formula: see text]-vibrational band built on the 1639.3[Formula: see text]keV level is observed, which confirms the previous suggestion from a [Formula: see text]-decay experiment. Systematical comparison supports the assignment for a two-phonon [Formula: see text]-vibrational band in [Formula: see text]Pd. Triaxial projected shell model calculations for the multi-phonon [Formula: see text] bands of [Formula: see text]Pd are in good agreement with the experimental data.

Collective Band Structures and Identification of One-Phonon and Two-Phonon γ-Vibrational Bands in 109Tc

The high spin states of the neutron-rich 109Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. The previously known yrast band based on the 7/2+ state is updated. A side band built on the 11/2+ state is expanded and a new band based on the 15/2+ state is identified. Band crossing in the yrast band occurs around ħω ≈ 0.36MeV. This band crossing is associated with the alignment of two h11/2 neutrons according to the cranked shell model calculations. The band based on the 11/2+ state is proposed as a candidate for the one-phonon γ-vibrational band, and the band built on the 15/2+ state is proposed as a candidate for the two-phonon γ-vibrational band. Other characteristics for the observed bands are discussed.

Identification of Two-Phonon γ-Vibrational Bands in Odd- A Nuclei at A ∼ 100 Region

Identification of Two-Phonon γ-Vibrational Bands in Odd- A Nuclei at A ∼ 100 Region

Reinvestigation of Collective Bands in 107Tc

The high spin states of a neutron-rich 107Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. The previous level scheme is updated. A collective band based on the π5/2− [303] orbital is confirmed and extended. Inconsistencies in the configuration assignments for a type of positive parity bands of odd-A 105,107,109Tc in the previous reports are clarified according to the g factor calculations. A new band based on the 1499.5 keV level in 107Tc is proposed as a two-phonon γ-vibrational band.

Gamma Vibrational Bands and Chiral Doublet Bands in A≈100 Neutron-rich Nuclei

The level structures of neutron-rich 105Mo,106Mo,108Mo and 110Ru nuclei in A ≈ 100 region have been carefully investigated by coincidence measurements of the prompt γ-rays populated in the spontaneous fission of 252Cf with the Gammasphere detector array. In 105Mo,one-phonon K=9/2 and two-phonon K=13/2 γ-vibrational bands have been identified. In 108Mo,one-phonon γ-vibrational band is expanded and two-phonon γ-vibrational band has been identified. Two similar sets of bands in 106Mo and 110Ru are observed to high spins,which have been proposed as the soft chiral γ-vibrational bands. The characteristics for these γ-vibrational bands and chiral doublet bands have been discussed.

Identification of one-phonon and two-phonon γ-vibrational bands in odd-Z103Nb nucleus

Collective bands in the neutron-rich 103Nb nucleus have been investigated by measuring prompt γ-rays following spontaneous fission of 252Cf. Three new bands have been identified. The band based on the 716.8 keV level is proposed as a candidate for the Kπ=9/2+ one-phonon γ-vibrational band, and the band built on the 1282.1 keV level is proposed as a candidate for the Kπ=13/2+ two-phonon γ-vibrational band. The two-phonon γ-vibrational band is the first such band identified in odd-Z nuclei.

Collective Band Structures in Neutron-Rich 108Mo Nucleus

High spin states in the neutron-rich 108Mo nucleus arestudied by measuring prompt γ-rays following thespontaneous fission of 252Cf with a Gammasphere detectorarray. The ground-state band is confirmed, and the one-phononγ-vibrational band is updated with spin up to 12 ℏ. A newcollective band with the band head level at 1422.4 keV is suggested asa two-phonon γ-vibrational band. Another new band is proposed asa two-quasi-proton excitation band. Systematic characteristics of thecollective bands are discussed.

Collective bands in 104,106,108Mo

We have used our analysis of γ-γ-γ data (5.7 × 1011 triples and higher folds) taken with Gammasphere from prompt γ rays emitted in the spontaneous fission of 252Cf to study the collective bands in 104,106,108Mo. The one-phonon and two-phonon γ-vibrational bands and known two-quasiparticle bands in neutron-rich 104,106Mo were extended to higher spins. The one-and two-phonon γ-vibrational bands have remarkably close energies for transitions from the same spin states and identical moments of inertia. Several new bands are observed and are proposed as quasiparticle bands in 104,106Mo, along with the first β-type vibrational band in 106Mo. The quasiparticle bands have essentially constant moments of inertia near the rigid-body value that indicate blocking of the pairing interaction. Candidates for chiral doublet bands in 106Mo are strong. These are the first reported chiral vibrational bands in an even-even nucleus.

High-Spin Structure in Neutron-Rich 108Ru Nucleus

High spin states in the neutron-rich 108Ru nucleus havebeen studied through measuring prompt γ-ray coincidences following thespontaneous fission of 252Cf with the Gammasphere detectorarray. The yrast band has been confirmed. The one-phonon γ-vibrationalband and the two-quasiparticle band based on the 5− levelhave been extended up to 13+ and 15−, respectively. Inaddition, two levels at 1644.8 keV and 1826.5 keV excitation energiesare newly identified and proposed to be themembers of a two-phonon γ-vibrational band. It is shown that the108Ru nucleus has triaxial deformation with parametersβ2~0.29 and γ = −22 degrees from the total Routhian surfacecalculations. The observed band crossing in the yrast band is due tothe alignment of a pair of h11/2 neutrons according to thecranked shell model calculations. The possible configuration for thetwo-quasiparticle band has been discussed.

Observation of Rotational Bands in Neutron-Rich 106Mo Nucleus

The rotational bands up to a spin of 16ℏ in the neutron-rich106Mo nucleus have been investigated by measuring high-foldprompt γ-ray coincidence events following spontaneous fissionof 252Cf with a Gammasphere detector array. The ground-stateband, the one-phonon and two-phonon γ-vibrational bands, aswell as a quasi-particle band have been confirmed and expanded. Theother four collective rotational bands, three proposed astwo-quasi-particle bands and one proposed as a β-vibrationalband, have been newly observed. The characteristics of thesecollective bands and the possible configurations for thequasi-particle bands are discussed.