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E2/M1 mixing ratios have been measured for transitions from states in the γ vibrational bands (I+γ) to states in the ground state bands (I+ or [I-1]+) of the neutron rich, even-even, deformed isotopes, 102,104,106,108Mo, 108,110,112Ru, and 112,114,116Pd, including from states as high as 9+γ. These measurements were done using the GAMMASPHERE detector array, which, at the time of the experiment, had 101 working HPGe detectors, arranged at 64 different angles. A 62 μCi source of 252Cf was placed inside GAMMASPHERE yielding 5.7 × 1011 γ-γ-γ and higher coincidence events. The angular correlations between the transitions from the γ-bands to the ground bands, and the pure E2 transitions within the ground band were then measured. These angular correlations yielded the mixing ratios, demonstrating that these transitions are pure or nearly pure E2, in agreement with theory. In order to correct for possible attenuation due to the lifetime of the intermediate state in these correlations, the g-factors of the intermediate states needed to be known. Therefore, the g-factors of the 2+ states in the ground state band have been measured. [ABSTRACT FROM AUTHOR]

Excited high spin states in 211At, 212Rn, 213Fr and 214Ra with N = 126 are reorganized and interpreted in terms of the stretched weak coupling of an octupole 3 − phonon. Nearly identical sequences of levels with ΔI = 3 and the parity change are found, for the first time, up to 25 − for 20 states of 214Ra, up to 35 − for 36 states of 212Rn and up to 53/2 + for 16 states of 213Fr. The stretched weak coupling of an octupole phonon is extended up to the highest excitation energy of 11355 keV for 212Rn which has the largest experimental B( E3) value of 44.1(88) W.u. for the 11 − → 8 2+ transition. The stretched weak coupling of an octupole 3 − phonon needs to be considered when single particle configurations are assigned to high spin states. Average octupole excitation energies of 657(51) keV for 211At, 1101(28) keV for 212Rn, 667(25) keV for 213Fr, and 709(25) keV for 214Ra are obtained. The calculated level enegies are in a good agreement with the experimental level energies within the error limit of 4.3%. [ABSTRACT FROM AUTHOR]

High-spin states of the neutron-rich 152Nd nucleus have been reinvestigated by measuring the prompt $ \gamma$ -rays in the spontaneous fission of 252Cf . The ground-state band and a side negative-parity band have been updated. A new band based on the 2243.7keV isomeric state has been identified. The half-life for the isomeric state has been measured to be 63(7)ns. The projected shell model is employed to study the band structure of this nucleus. The results show that the calculated levels of the bands are in good agreement with the experimental ones, and the isomeric state and the negative-parity band are based on the proton $ \pi$5/2-[532] ⊗ $ \pi$9/2+[404] and neutron $ \nu$3/2-[521] ⊗ $ \nu$5/2+[642] two-quasiparticles configurations, respectively. [ABSTRACT FROM AUTHOR]

A new experiment devoted to the fission of 252Cf is described. It continued a series of our experiments based on correlation measurements of γ rays emitted by fission fragment pairs. The measurements of γ-γ and γ-γ-γ coincidences were done at Gammasphere with closed 252Cf sources. The open source was used for the first time in the last experiment. Fission fragment detectors were arranged in the center hole of Gammasphere. Correlations between fission fragment masses, total kinetic energy, and γ rays were observed. The first, preliminary results of data analysis are discussed. [ABSTRACT FROM AUTHOR]

The hot bimodal fission of 252Cf is reexamined with new high-statistics data. We constructed a γ-γ-γ coincidence cube for binary fission and LCP-gated γ-γ matrix for ternary fission. By identifying the secondary fission fragments from their γ-ray transitions, we measured the yields for various fission splits. The normal neutron yield distribution is found to be Gaussian for Xe-Ru. However, the binary fission split of Ba-Mo is found to exhibit a bimodal neutron distribution with the “hot mode” corresponding to ≈3.1% of the total yield. In α ternary fission, the first measurements of yields for specific fission splits are presented. The Te- α-Ru and Xe- α-Mo neutron yields fit well with a single mode, but the Ba- α-Zr split shows evidence for an enhanced hot mode with an intensity of ≈13.8% of the normal mode. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

High-spin states in neutron-rich 106Mo were investigated by detecting the prompt γ-rays in the spontaneous fission of 252Cf with Gammasphere. Several new bands are observed. Two sets of Δ I = 1 bands in 106Mo are found to have all the characteristics of a new class of chiral vibrational doublets. Tilted axis cranking calculations support the chiral assignment and indicate that the chirality is generated by neutron h11/2 particle and mixed d5/2, g7/2 hole coupled to the short and long axis, repectively. [ABSTRACT FROM AUTHOR]

For the first time, average angular momenta of the ternary fission fragments100, 102Zr,106Mo,144, 146Ba and138, 140, 142Xe from the α-accompanied fission of252Cf were obtained from relative intensities of prompt γ-ray transitions with the use of the statistical model calculation. Average values of the angular momenta were compared with the corresponding values for the same fission fragments from the binary fission of252Cf. Results indicate the presence of a decreasing trend in the average values of angular momenta induced in ternary fission fragments compared to the same binary fission fragments. On the average, the total angular momentum extracted for ternary fission fragments is ∼1.4 ℏ lower than in binary fission. Consequently, results indicate that the mechanism of the ternary α-particles emission may directly effect an induction of angular momenta of fission fragments, and possible scenarios of such mechanisms are discussed. Further, the dependence of the angular momenta of106Mo and140Xe on the number of emitted neutrons from correlated pairs of primary fragments was obtained also showing a decreasing dependence of average angular momenta with increasing number of emitted neutrons. Consequences are briefly discussed. [ABSTRACT FROM AUTHOR]

The spontaneous fission (SF) of [sup 252]Cf has been studied via γ-γ-γ coincidence and light charged particle—γ-γ coincidence with Gammasphere. The yields of correlated Mo-Ba pairs in binary fission with 0-10 neutron emission have been remeasured with an uncompressed cube. The previous hot fission mode with 8-10 neutron emission seen in the Mo-Ba split is found to be smaller than earlier results but still present. New 0n binary SF yields are reported. By gating on the light charged particles detected in ΔE-E detectors and γ-γ coincidence with Gammasphere, the relative yields of correlated pairs in alpha ternary fission with zero to 6n emission are observed for the first time. The peak occurs around the α2n channel. A number of correlated pairs are identified in ternary fission with [sup 10]Be as the light charged particle. We observed only cold, 0n [sup 10]Be and little, if any, hot, xn [sup 10]Be channels. [ABSTRACT FROM AUTHOR]

The levels in [sup 162]Gd were identified in spontaneous fission studies. Its transition energies are remarkably similar to those in [sup 160]Gd. From that work, an analysis of yrast bands in even-even proton to neutron-rich Ba to Pb nuclei led to the discovery of a new phenomenon, shifted identical bands (SIB). SIBs are yrast bands in neighboring nuclei (a, b) with moments of inertia which are identical when shifted by a constant amount κ, so J[sub 1a](1 + κ) = J[sub 1b], from 2[sup +] to 8[sup +] and higher to 16[sup +]. Out of over 700 comparisons, 55 SIBs were found from stable to the most neutron-rich Ce-W nuclei with &κmacr; between 1.5% and 13%, where the spread in κ is less than ±1%, and only four identical bands (&κmacr; ≅ 0). As examples, we found for [sup 158]Sm-[sup 160]Gd, &κmacr; = (-3.2[sup +0.1, sub -0.2]) % (where the ± is the total spread in κ from -3.1 to -3.4); [sup 156]Nd-[sup 160]Gd, 10 (-10.6 [sup +0.4, sub 0.2])%; [sup 158]Sm-[sup 160]Sm, (3.4[sup +0.5, sub -0.3])%. The J[sub 1] values were fitted to a variable moment of inertia model with parameters J[sub 0] and C whose values correlate with the SIB J[sub 1] values. The SIBs are not correlated either with deformation or with the N[sub p]N[sub n] product of the IBA model. [ABSTRACT FROM AUTHOR]

Half-lives ( T1/2) of several states which decay by delayed γ transitions were determined from time-gated triple γ coincidence method. We determined, for the first time, the half-life of 330.6 + x state in 108Tc and the half-life of 19/2- state in 133Te based on the new level schemes. Five half-lives of 95, 97Sr, 99Zr, 134Te and 137Xe are consistent with the previously reported ones. These results indicate that this new method is useful for measuring the half-lives. [ABSTRACT FROM AUTHOR]

Measurement of fine structure in proton emission allows one to deduce the composition of the parent and daughter state’s wavefunction populated by proton emission. This paper presents new experimental data on the fine-structure decay of 146Tm, and a new interpretation of its decay properties. [ABSTRACT FROM AUTHOR]

New level schemes of 99, 101Y and 101, 105Nd are established based on the measurement of prompt γ-rays from the fission of 252Cf at Gammasphere. Triaxial-rotor-plus-particle model calculations and fitting suggest that in the A ≈ 100 neutron-rich nuclei triaxial shape is prevalent in the region with Z > 41. [ABSTRACT FROM AUTHOR]

By using different time-gated triple γ coincidence data, the half-lives ( T1/2) of several short lived states in neutron-rich nuclei have been studied. The first excited states in the ground state bands often decay by delayed γ emission. By creating triple γ coincidence spectra with time windows of 8, 16, 20, 28, and 48 ns, we have studied states with half-lives below 10 ns. The estimated half-lives of 102Zr, 137Xe, and 143Ba are in reasonable agreement with previously reported values. We extract the first estimates of the half lives of the 2+ states in 104Zr and 152Ce. [ABSTRACT FROM AUTHOR]

Triple-γ coincidence data were used to study the γ-vibrational bands to 14+ in 104-106Mo, to 13+ in 108,110Ru and 17+ in 112Ru, and to 13+, 15+ in 112-116Pd. The even-odd spin energy level splittings show rapid variations with spin and neutron number in these nuclides. With one exception, the Sm-Pt nuclei show no such reversal and much smaller staggering. [ABSTRACT FROM AUTHOR]

From prompt γ-γ-γ coincidence studies with a 252Cf source, the yrast levels were identified from 2+ to 16+ and 14+ in neutron-rich 162,164Gd, respectively. Transition energies between the same spin states are higher and moments of inertia lower at every level in N = 100 164Gd than in N = 98 162Gd. These observations are in contrast to the continuous decrease in the 2+ energy to a minimum at neutron midshell ( N = 104) in Er, Yb, and Hf nuclei. [ABSTRACT FROM AUTHOR]