[en] The level structures of neutron-rich Xe isotopes were determined by observing prompt gamma-ray coincidences in ²⁴⁸Cm fission fragments. A 5-mg ²⁴⁸Cm, in the form of ²⁴⁸Cm-KCl pellet, was placed inside Eurogam array which consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. Transitions in Xe isotopes were identified by the appearance of new peaks in the γ-ray spectra obtained by gating on the gamma peaks of the complementary Mo fragments

[en] Krypton and xenon isotopes, produced in the thermal neutron fission of ²³⁵U, were investigated by electromagnetic separation of chemically pure noble gases emanating from a uranium oxide-barium stearate target and introduced into an on-line mass-separator, the SOLIS. The separated isotopes were beta counted and the transfer function and half lives of the separated isotope and its precursor in the target were calculated. Two new isotopes ⁹³Kr and ¹⁴³Xe were detected and characterized by their half lives (0.2 + 0.02 and 0.3 + 0.03 sec, respectively). In gamma ray measurements, the prominent gamma peaks of ⁹³Kr and ⁹³Rb were identified and their relative intensities calculated. Relative, independent fission yields of the heavy isotopes of Kr and Xe were obtained by analyzing the beta decay curves obtained at similar operating conditions. For the lighter isotopes, e.g. ⁸⁷Kr, ¹³⁹Xe, absolute yields were obtained by calculating the ratio of cumulative yields of the halogen precursor to the independent yield of the noble gas, from curves describing the growth of beta activity as a function of irradiation time. The fission yields obtained in this work are systematically higher than those predicted by the ''normal'' Gaussian distribution suggested by Wahl. Since both Kr and Xe have even numbers of protons, it was suggested that the high yields are due to preservation of proton pairs in the fission of the even Z nucleus. Comparison of other published fission yields with the ''normal'' distribution showed an average enhancement of 22(+-7)% in the yields of even Z nuclei with a corresponding decrease in the yields of odd Z nuclei. (H.K.)

[en] Excited states in ¹⁴³Xe, populated in spontaneous fission of ²⁴⁸Cm, are studied by means of γ spectroscopy using the EUROGAM 2 Ge array. We identify three rotational bands in ¹⁴³X: a decoupled band originating from the i_13/2 neutron excitation, a strongly coupled band based on the 5/2^- ground state, and a decoupled band based on the 322.9-keV level with spin 9/2. The new excitation scheme of ¹⁴³Xe is compared to quasiparticle-rotor model calculations, performed with a reflection-symmetric potential.

[en] The β decay of the neutron-rich nuclides, 40-s /sup 139/Xe, 1.7-s /sup 141/Xe, and 0.4-s /sup 143/Xe to levels of odd-Z /sup 139/Cs, /sup 141/Cs, and /sup 143/Cs, respectively, has been studied using sources isolated from fission products by on-line mass separation. The data collected include gamma-ray and conversion electron singles spectra as well as gamma-ray coincidence and angular correlation spectra. New levels have been identified in /sup 139/Cs including a doublet at 393 keV, and new spin and parity assignments are proposed. New data are presented for /sup 141/Cs levels in support of an earlier proposed level scheme by Talbert and Cook. Evidence for a 0.4-s half-life for /sup 143/Xe has been found, and a level at 90 keV is proposed for /sup 143/Cs. The resulting level structures for the neutron-rich Cs nuclides are compared with level structures of other odd-Z neutron-rich nuclides and neutron deficient Cs nuclides. The transition from the structure observed near the closed N = 82 neutron shell to deformed structures described by Nilsson model orbitals is discussed

[en] The fractional cumulative yields of ⁹¹Kr, ⁹²Kr, ⁹³Kr, ¹³⁹Xe, ¹⁴⁰Xe, ¹⁴¹Xe, ¹⁴²Xe, and ¹⁴³Xe in the reactor neutron induced fission of ²³²Th were determined radiochemically using a continuous chemical separation of these rare gases from the remaining fission products by diffusion through a layer of Mg-stearate. The data obtained are compared to the literature data and discussed in the light of the Z_p model of WAHL. The following parameters are obtained for the charge distribution in ²³²Th fission: Charge polarization ΔZ (A'=140)=-0.45±0.01, width of Gaussian dispersion σ_Z=0.54±0.01, even-odd proton effect (EOZ)=1.30±0.03, even-odd neutron effect (EON)=1.08±0.03 and the slope parameter S=-0.004±0.004. (orig.)

No abstract available

[en] Laser spectroscopy measurements have yielded a wealth of new information about the moments and charge radii of unstable isotopes. The procedures of evaluating these moments from the magnetic dipole and electric quadrupole terms of the hyperfine structure are discussed. Examples are presented, with emphasis on the isotopic chains of odd-proton nuclei, and their essential features are put into the context of current theoretical model descriptions for spherical and deformed nuclei. Finally, new developments of extremely sensitive experimental techniques are discussed with regard to an application to nuclei very far from stability. (orig.)

[en] Beta-decay half-lives and delayed-neutron emission probabilities of the neutron-rich noble-gas isotopes ^94-99Kr and ^142-147Xe have been measured at the PSB-ISOLDE facility at CERN. The results are compared to QRPA shell-model predictions and are used in dynamic calculations of r-process abundances of Kr and Xe isotopes

[en] Experimental nuclear structure information, based upon radioactive decay and nuclear raction studies, is presented for all known nuclides with mass 143. The arguments for Jπ assignments and the level energies often derived by the evaluators are given in the ''Adopted Levels'' sections. The measurement techniques, methods of analysis, and assumptions used by the authors are indicated by evaluators' comments with various data sections

[en] A search for octupole deformation in neutron-rich Xe isotopes has been conducted by prompt gamma-ray spectroscopy of secondary fragments produced in the spontaneous fission of ²⁴⁸Cm. The spectrometer consisted of the Eurogam 1 array and a set of 5 LEPS detectors. Level schemes were constructed for Xe isotopes with mass number ranging from 140 to 144 and excited states for ^143,144Xe nuclei were observed for the first time. None of the level schemes exhibit an alternating parity quasimolecular band, a feature usually expected in nuclei in which octupole correlation effects are strong enough to produce stable octupole deformation. For several isotopes, structures observed in the level schemes are consistent with an octupole softness of the nuclei. (orig.)