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Analysis of high statistics triple coincidence fission γ data from 252Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for 82Ge, 118,120,122Cd and 114,115Rh. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. These Cd isotopes may have triaxial deformations. High-spin level schemes of 114,115Rh have been established for the first time. The existence of a relatively large signature splitting and an yrare band shows typical features of a triaxially deformed nucleus. Possible excited deformed rotational bands are observed, for the first time, in 82Ge. From the multipole mixing ratio measurement, the ground state configurations of 109,111Ru, as well as excited states in 103,107Mo and 111Ru were determined.

With a very high statistics data set with 5.7×1011 triple and higher fold γ coincidences from the spontaneous fission of 252Cf, a wealth of fascinating new collective motions in nuclei with A = 100–112 have been observed. Nothing was known previously about one‐ and two‐phonon γ‐bands in odd‐A nuclei. We discovered the first one‐and two‐ phonon γ vibrational bands in an odd N‐even Z nucleus, 105Mo. The energies of the one‐ and two‐ phonon bands in 104Mo, 105Mo, 106Mo and 108Mo were recently studied and are remarkably similar in energies. The first chiral doublet bands in e‐e nuclei were observed in triaxial 106,108Mo and 110,112Ru while such chiral band in 108Ru are perturbed by its γ‐soft shape. The experimental evidences, including our recent angular correlation studies are presented along with what these new bands are telling us about the evolving collective structures and deformation in this region.

The high spin states of neutron‐rich nuclei in A∼110 region have been carefully investigated by measuring prompt γ‐γ‐γ coincident measurements populated in the spontaneous fission of 252Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one‐phonon‐ and two‐phonon γ‐vibrational bands in odd‐A 103Nb, 105Mo and 107Tc, the chiral doublet bands in even‐even 106Mo, 110Ru and 112Ru, and the pseudospin partner bands with in 108Tc. The characteristics of these band structures have been discussed.The high spin states of neutron‐rich nuclei in A∼110 region have been carefully investigated by measuring prompt γ‐γ‐γ coincident measurements populated in the spontaneous fission of 252Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one‐phonon‐ and two‐phonon γ‐vibrational bands in odd‐A 103Nb, 105Mo and 107Tc, the chiral doublet bands in even‐even 106Mo, 110Ru and 112Ru, and the pseudospin partner bands with in 108Tc. The characteristics of these band structures have been discussed.

In an experiment carried out at the 4π Ge detector facility Gammasphere the yields of ternary fission events of 252Cf accompanied by the emission of He, Be and C LCPs were measured. For the first time independent yields were measured for 59 pairs of secondary fragments of the He ternary fission and for many fission fragments detected together with the He, Be and C LCPs. With a reasonable assumption that the detected LCPs predominantly are 4He, 10Be and 14C their yields and the charge distributions of fission fragments were conjointly analyzed in terms of the “energy cost” concept first suggested by Halpern.

With our high statistics γ‐γ‐γ data set taken with Gammasphere, we have identified a variety of new phenomena in A = 100–112 nuclei. The one‐ and two‐ phonon γ bands in 104,106Mo have been extended and similar bands identified in 108Mo and for the first time in both an odd N nucleus, 105Mo and an odd Z nucleus, 103Nb. The one‐ and two‐ phonon γ band energy levels in 104,105,106,108Mo are remarkably similar with a trend toward lower energy as N increases. In 108,110,112Ru the one phonon γ bands show a completely different behavior from 104–108Mo with very large odd‐even spin level energy staggering in 112Ru. Our data indicate a maximum triaxiality around 112Ru. In 100Nb which lies between N = 58 and 60 where a sudden shift from spherical to superdeformed structures occurs in Sr and Zr nuclei, we have discovered a Kπ = 1+ deformed ground state band. In 108Tc, we found the first pseudospin partner bands with nearly degenerate energies in this mass region.

Fine structure in proton emission from the deformed states 141g.s.Ho (T1/2 = 4.1 ms) and 141mHo (T1/2 = 7.4 μs) has been discovered at Oak Ridge by detecting fusion evaporation residues with the Recoil Mass Spectrometer, Si‐detectors and digital signal processing electronics. The branching ratios to the first 2+ excited state in 140Dy were measured to be Ipg.s.(2+) = 0.9±0.1% and Ipm(2+) = 1.7±0.5%. A comparison of the available calculations to the experimental values calls for further development of the theoretical models.

The alpha decay chain 109Xe→105Te→101Sn was first identified at the Holifield Radioactive Ion Beam Facility. Recent developments in digital electronics enabled the detection of both alpha decays despite the short half‐life of 105Te. The development of the software algorithm responsible for extracting the double‐alpha events from the experimental data is ongoing. The possibility of using the derivative of the double‐alpha pulse to selectively identify double alpha pulses shows promise and is being developed.

The systematics of the πh11/2⊗νh11/2 and πh11/2⊗νs1/2 isomeric configurations were studied for the odd‐Z N = 77 isotones near the proton dripline. The spin and parity of Iπ = 8+ and 5− were deduced for the isomers in 140Eu and 142Tb. No evidence for the expected 1+ ground‐state was found in the 144Ho decay data. The proton emission from 146Tm was restudied and the spin and parity values of Iπ = 10+ and 5− were established for 146mTm and 146gsTm, respectively. The interpretation of the observed decay properties and structure of the proton‐emitting states was made by accounting for deformation and proton and neutron coupling to the core excitations.

In an experiment at the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility, the very small α‐decay branch of 109I, bα = (1.4±0.4)⋅10−4, has been measured. The Qα‐value for this transition allowed for the determination of Qp(105Sb) = 356±22 keV, about 130 keV lower than previously claimed. This difference increases the partial half‐life for proton decay by several orders of magnitude, making the probability of observing direct proton decay of 105Sb very small, much below any previous experimental limit. The results and consequences for the astrophysical rp‐process are discussed.

Production of nuclei above 100Sn in fusion‐evaporation reactions between 58Ni beam and 54Fe target was investigated. Reaction products were studied at Oak Ridge by means of the Recoil Mass Spectrometer and charged particle detection. The yields for the 2n, pn, 3n, p2n, 2pn, p3n and 2p2n fusion‐evaporation channels were measured. These experimental results were used to verify the predictions of the statistical model code HIVAP. The optimum energy for the 54Fe(58Ni,4n)108Xe reaction allowing detection of the 108Xe‐104Te‐100Sn alpha decay chain is deduced as 240 MeV.

High spin states in 136,137La and 148Ce nuclei have been investigated. The new level schemes for these nuclei have been established. In 136La, observed band crossing as well as the signature splitting and inversion in πh11/2⊗νh11/2 band has been discussed. Other two bands were proposed as oblate deformation with γ ∼ −60°. In 137La, several new bands have been established. The band crossing and oblate deformation have been discussed. In 148Ce, the double octupole deformation bands with s = +1 and s = −1 have been proposed.

A series of experiments has been performed to measure the dependence on the fragment mass and total kinetic energy of the average number and energy of prompt neutrons emitted from 235U and 239Pu fission fragments in thermal neutron induced fission. The experiments were carried out using neutrons from the PNPI WWR‐M research reactor in Gatchina. For the 239Pu target the fragment — neutron correlation measurement was also performed at the first resonance. In this case the neutron energy of the strong resonance at 0.296 eV was selected by a Sm filter which was arranged in the neutron flux from the reactor. The description of the experimental set‐up and some preliminary results of the average number and kinetic energies of prompt neutrons as a function fragment mass are presented in this article.

Decay studies on rare earth nuclei around the proton drip line have been performed by means of the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility in Oak Ridge. The proton emission from the odd‐odd N=77 isotone 146Tm was reinvestigated, resulting in the assignment of the 1.01 MeV proton line to the decay of a short‐lived 146Tm state. A new proton radioactivity of 144Tm was identified. The decays of isomeric levels in the N=77 isotones, 140Eu, 142Tb and 144Ho were remeasured using γ and electron detectors. The analysis of the structure of studied nuclei, which accounts for the coupling between the protons and neutrons and for core excitations, is presented.

An experiment was performed at the National Superconducting Cyclotron Laboratory at Michigan State University to investigate β‐ and isomer decay properties of several isotopes in the vicinity of 78Ni. The identification of an (8+) isomer in 76Ni was confirmed and its deexcitation cascade identified; the β‐decay of 71–73Co was reinvestigated and that of 74Co studied for the first time. First evidence of β‐delayed neutron emission in neutron‐rich cobalt isotopes was also obtained. Preliminary results are reported.

The mass A = 140 products of the 54Fe (315 MeV) + 92Mo reaction were selected by a recoil mass spectrometer and studied in a recoil ‐ delayed γ‐γ coincidence experiment. A new 7 μs isomer was identified in the drip line nucleus 140Dy. Five cascading γ transitions were assigned to the decay of the Iπ = 8− {v9/2−[514] ⊗ v7/2+[404]} K isomer via the ground state band transitions. The established structure of 140Dy is discussed with reference to the fine structure in proton decay of 141Ho.

The observation of fine structure in proton emission allows one to measure the composition of the parent state’s wavefunction and the deformation of the daughter state. A systematic study of proton‐unbound nuclei in the rare earth region is ongoing at the HRIBF. Newly discovered fine structure in the decays of 145Tm and 141Ho are discussed, as well as advances in our experimental equipment.

A new 7 μs isomer in the drip line nucleus 140Dy was selected from the products of the 54Fe (315 MeV) + 92Mo reaction by a recoil mass spectrometer and studied with recoil ‐ delayed γ‐γ coincidences. Five cascading γ transitions were interpreted as the decay of an Iπ = 8− {v9/2−[514] ⊗ v7/2+[404]} K isomer via the ground state band.

New analyses of spontaneous-fission gamma data from our 252Cf Gammasphere runs of 1995 and 2000 have identified new transitions and given improved transition energy and intensity values for known transitions in even-odd fission-product nuclei just beyond the 82-neutron closed shell. New level schemes of N=83 isotones 139Ba83 and 135Te83 and of N=85 isotones 141Ba85, and 139Xe85 are established. Single-particle (hole) excitations and couplings, core excitations, and octupole excitations are assigned to these isotones. A regular sequence found in 135Te is interpreted as a shears band within the tilted-axis cranking model of Frauendorf. The level systematics of N=85 isotones indicate that the octupole excitation moves to higher excitation energy as the Z=50 shell is approached.

We identified γ transitions in several neutron‐rich nuclei near 132Sn produced in the spontaneous fission of 252Cf. These are of interest because they can test shell model calculations. These nuclei are 139Ba, 133,135Te, and 121,123Cd. Excited states in neutron‐rich 133Te exhibit four types of particle‐hole bands built on the known 334.3 keV isomer in 133Te. The yrast and near yrast particle‐hole states observed up to 6.2 MeV in 133Te have characteristics quite similar to those in 134Te. The band starting at 5.214 MeV is assigned as a neutron particle‐hole excitation of the double magic core nucleus, 132Sn and is a candidate for a tilted rotor band. Theoretical shell model calculations show good agreement with the experimental states up to 4.3 MeV. The new level scheme of 139Ba includes 11 new transitions and 10 new levels and is compared with the 83‐neutron isotone 135Te. In 135Te, a tilted rotor band, also, is proposed. Excited states built on the 11/2− isomeric states in neutron‐rich 121,123Cd are iden...

A new region of stable octupole deformation was predicted to occur with its center around the reinforcing shell gaps for β3∼0.15 at Z=56, N=88, and with 56145Ba89 was predicted to be a prime candidate for stable octupole deformation. Evidence for stable octupole deformation was found in 144Ba, 146Ce and expanded to include odd-A 143Ba and other neighboring isotopes but was not observed in 145Ba. Recently we found evidence for the rotational enhancement of stable octupole deformation in 145,147La. In a reinvestigation of 145Ba, two new bands were discovered that are connected by enhanced, intertwined E1 transitions to two different previously known bands in 145Ba. These new data support the predicted presence of octupole deformation in 145Ba, which is rotation-enhanced above about spin 19/2. In both 145La and 145Ba, the low spin ground bands are built on a symmetric rotor shape and at intermediate spins there are shifts to the yrast bands having asymmetric octupole shape. These are the first examples of th...

Proton radioactivity studies performed at the Holifield Radioactive Ion Beam Facility (HRIBF) within the last few years are reviewed. The discovery of five new proton radioactivities 140Ho, 141mHo, 145Tm, 150mLu and 151mLu is presented together with a recent observation of fine structure in proton emission from 146gs,mTm. These proton emitters were produced by means of fusion-evaporation reactions and studied with the HRIBF Recoil Mass Separator and detection system based on a Double-sided Silicon Strip Detector. For 113Cs and 151Lu, the studies of level structure were extended beyond the proton-emitting states via the measurements with a clover array CLARION using Recoil Decay Tagging.

We studied the proton emission from 69145Tm77 and observed three new transitions. New transitions at 0.89 and 0.93 MeV have half-lives similar to that of the previously observed transition at 1.19 MeV, while a new transition at 1.02 MeV has a half-life similar to that of the previously observed transition at 1.12 MeV. These new transitions indicate the population of excited neutron single-particle states in 68145Er77.

A double-sided Si-strip detector system has been installed and commissioned at the focal plane of the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility. The system can be used for heavy charged particle emission studies with half-lives as low as a few μsec. In this paper we present identification and study of the decay properties of the five new proton emitters: 140Ho, 141mHo, 145Tm, 150mLu and 151mLu.

Evidence for stable octupole deformation in neutron-rich nuclei bounded by Z=54–58 and N=85–92 is described. More vibrational type octupole modes are observed to either side of this region in 140Ba and 152,154Nd. The largest stable octupole deformation (β3∼0.1) is reported in 144Bagg. The theoretically predicted quenching (β3→0) of stable octupole deformation with increased rotation is observed in 146Ba. There is good agreement between theory and experiment for the strongly varying electric dipole moments as a function of mass for 142–148Ba. In odd-A 143Ba and odd-Z, 145La, two pairs of positive and negative parity bands with opposite spins, parity doublets are observed. In 145La the ground band with symmetric shape coexists with the asymmetric octupole shape which stabilizes above about spin 19/2+. The isotope 109Mo was identified and a new region of stable octupole deformation is identified in 107,109Mo centered around N=64–66 as earlier predicted. This is the first case of stable octupole deformation i...

Yields of correlated fragment pairs were obtained in spontaneous fission of 242Pu. Charge, mass and neutron multiplicity distributions of fragment pairs were determined and compared to available data. The yield of cold fission without neutron emission was determined to about 10% for the set of observed correlated fragment pairs.

Prompt γ-γ-γ coincidence studies following spontaneous fission of 252Cf were carried out at Gammasphere first with 36 and later with 72 Ge detectors. Yields and neutron multiplicities were measured directly for Sr-Nd, Zr-Ce Mo-Ba, Ru-Xe, and Pd-Te correlated pairs. A new hot fission mode was discovered going via only 108Mo-144Ba, 107Mo-145Ba, and/or 106Mo-146Ba pairs where one or more of 144,145,146Ba are hyperdeformed at scission with 3:1 axis ratio. For the first time correlated pairs involved in cold ternary fission were observed with the third particle 4He, possibly 6He, and 10Be. The 142-146Ba data provide evidence for the predicted disappearance of stable octupole deformation at high spins. New level structures and isotopes include new octupole deformations, identical bands and other structures.

Extension of our knowledge of N=Z nuclei up to Mo4284 are reviewed. Only γ-ray singles data are available for Ge64 to Mo84, so more definitive tests of theoretical predictions of shape coexistence and deformation changes among them are not possible with present data. The limitations of current facilities to probe in the necessary detail the N=Z line and to extend it further are discussed. A new generation recoil mass spectrometer has been designed for HHIRF to overcome present limitations. The key new feature is a momentum achromat in front of a traditional RMS. A proposed radioactive beam facility for HHIRF, along with the new RMS is shown to open up studies of the N=Z line to Sn50100 and beyond.

A proposed recoil mass spectrometer of high rigidity, large solid angle acceptance, and good mass resolution for use with the HHIRF accelerators at ORNL is described.

Now magic numbers for deformed shapes are established at N and Z of 38 and N of 60. These shell gaps at large deformation (β∼0.4) are magic when the proton and neutron shell gaps reinforce each other. Other shell gaps for 34 and 36 are predicted to be important for oblate deformation. The competition between these oblate and the 38 prolate gaps as well as the 40 spherical shell gap are considered. In 71Se coexistence of oblate (β∼0.24) and large prolate (β∼0.4) shapes are observed. In 72Se the excited prolate band with large deformation which coexists with the near‐spherical ground state is found to dominate the yrast spectrum to 28+. The moment of inertia of this band is essentially that of a rigid body. This moment of inertia supports the suggestion that the ‘‘super deformation’’, β∼0.4, being observed in this region may be associated with a collapse of pairing.

The UNISOR on‐line nuclear orientation facility consists of a He3–He4 dilution refrigerator on line to the isotope separator. Nuclei are implanted directly onto a target foil soldered to the bottom accessed cold finger of the refrigerator. A 1.5 T superconducting magnet polarizes the ferromagnetic target foils and determines the axis of symmetry. Up to eight gamma detectors can be positioned around the refrigerator, each 9 cm from the target. A unique feature of this system is that the k=4 term in the directional distribution function can be deduced so that a single solution for the mixing ratio can be found.