J. B. Fitzgerald

Rotational bands in the mass 100 region

Abstract Rotational bands up to spin of ≈10 h have been studied in even-even and odd- A nuclei in the mass 100 region, by observing prompt γ-rays from the spontaneous fission of 248 Cm. Transitions in the neutro-rich nuclei 103 Zr, 104 Zr, 107 Mo and 108 Mo have been observed for the first time, and evidence for a band in 105 Nb is presented. Rotational bands are also reported in 98–100 Sr, 99,101 Y, 100–102 Zr, 101,103 Nb and 102–106 Mo. In most cases these bands have been extended to much higher spins than previously known. The data on the even-even nuclei provide information on deformation trends in this region. The level structures of the odd- A nuclei indicates which Nilsson orbitals lie close to the Fermi level. Bands based on the 5 2 + [422] and 5 2 − [303] configurations are identified in the odd- A nuclei with Z = 39 and 41. Evidence is presented that certain bands observed in N = 61 and 63 nuclei are built on the 5 2 − [532] configuration, and the role of the neutron h 11 2 orbital in stabilizing the deformation in this region is discussed.

New neutron-rich nucleiZr103,104and theA∼100 region of deformation

Partial decay schemes in the neutron-rich nuclei {sup 103}Zr and {sup 104}Zr have been measured for the first time and rotational bands in {sup 100--102}Zr have been extended to spins of up to 10{h bar} by observing prompt {gamma} rays from the spontaneous fisson of {sup 248}Cm. These nuclei are among the most deformed known at low spin and excitation energy. The level structures in the odd-{ital A} nuclei show that the {ital h}{sub 11/2} intruder orbital plays an important role in stabilizing the deformation in this region.

New neutron-rich nuclei sup 103,104 Zr and the A similar to 100 region of deformation

Partial decay schemes in the neutron-rich nuclei {sup 103}Zr and {sup 104}Zr have been measured for the first time and rotational bands in {sup 100--102}Zr have been extended to spins of up to 10{h bar} by observing prompt {gamma} rays from the spontaneous fisson of {sup 248}Cm. These nuclei are among the most deformed known at low spin and excitation energy. The level structures in the odd-{ital A} nuclei show that the {ital h}{sub 11/2} intruder orbital plays an important role in stabilizing the deformation in this region.

New neutron-rich nuclei Zr 1 0 3 , 1 0 4 and the A ∼100 region of deformation

Partial decay schemes in the neutron-rich nuclei {sup 103}Zr and {sup 104}Zr have been measured for the first time and rotational bands in {sup 100--102}Zr have been extended to spins of up to 10{h bar} by observing prompt {gamma} rays from the spontaneous fisson of {sup 248}Cm. These nuclei are among the most deformed known at low spin and excitation energy. The level structures in the odd-{ital A} nuclei show that the {ital h}{sub 11/2} intruder orbital plays an important role in stabilizing the deformation in this region.

New nucleus sup 142 Xe: Test of the N sub p N sub n scheme

Excited states in the neutron-rich nucleus {sup 142}Xe have been determined by observing prompt {gamma} rays in fragments from {sup 248}Cm spontaneous fission. Estimates of the lowest excited-state energies in {sup 142}Xe based on normal systematics differ considerably from those derived from the {ital N{sub p}N{sub n}} scheme. Experimental values are in good agreement with the {ital N{sub p}N{sub n}} scheme and illustrate its predictive power in this mass region.

New nucleusXe142: Test of theNpNnscheme

Excited states in the neutron-rich nucleus {sup 142}Xe have been determined by observing prompt {gamma} rays in fragments from {sup 248}Cm spontaneous fission. Estimates of the lowest excited-state energies in {sup 142}Xe based on normal systematics differ considerably from those derived from the {ital N{sub p}N{sub n}} scheme. Experimental values are in good agreement with the {ital N{sub p}N{sub n}} scheme and illustrate its predictive power in this mass region.

New nucleus Xe 142 : Test of the N p N n scheme

Excited states in the neutron-rich nucleus {sup 142}Xe have been determined by observing prompt {gamma} rays in fragments from {sup 248}Cm spontaneous fission. Estimates of the lowest excited-state energies in {sup 142}Xe based on normal systematics differ considerably from those derived from the {ital N{sub p}N{sub n}} scheme. Experimental values are in good agreement with the {ital N{sub p}N{sub n}} scheme and illustrate its predictive power in this mass region.

Reflection-Asymmetric Shapes in Nuclei

In the last few years, theoretical calculations and experimental results have established that nuclei in the mass 224 and Z = 56, N = 88 regions possess reflection-asymmetric (octupole) shapes. In both regions it is found that even-even nuclei are reflection symmetric in their ground states. However, these nuclei develop octupole deformation with rotation. Recently we have studied such phenomena in neutron-rich Ba and Ce nuclei produced in spontaneous fission. Detailed properties of these nuclei will be discussed.