[en] Angular correlation measurements were made on gamma-ray cascades in ¹⁴⁰Ba, ⁹⁰Sr, and ¹⁴⁰Cs. These fission-product activities were isobarically enhanced from Kr and Xe noble-gas parents, which were mass-separated by the TRISTAN isotope separator system. Levels in ¹⁴⁰Ba were populated from the 64-sec decay of ¹⁴⁰Cs, and in ¹⁴⁰Cs from the 14-sec decay of ¹⁴⁰Xe. Levels in ⁹⁰Sr were populated from the 2.7-min decay of ⁹⁰Rb, which was populated from the decay of ⁹⁰Kr. The most intense transitions were measured in coincidence with the first excited state to ground state transition in even-even ¹⁴⁰Ba and ⁹⁰Sr. The two-parameter mode of data accumulation was used to study cascades with transitions in coincidence with the 806-keV and 989-keV transitions in odd-odd ¹⁴⁰Cs. In the study of cascades in ¹⁴⁰Ba definite spin assignments were made for eight levels, and tentative spin assignments for five levels. For ⁹⁰Sr definite spin assignments were made for eight levels, and tentative assignments for six levels. A definite 1- spin-parity assignment was made for the 103-keV level in ¹⁴⁰Cs, and tentative assignments were made for five other levels. Values are given for the angular correlation coefficients, and limits of multipolarity mixing ratios are given where applicable. (44 figures, 3 tables) (U.S.)

[en] Average delayed-neutron energies for 16 isotopes of Br, Rb, I, and Cs have been measured by means of detector ring counting rate ratios in a polyethylene-moderated neutron counter system. An on-line mass spectrometer facility was used to give chemically and mass separated sources of delayed-neutron precursors. A simple expression predicts general trends of the average delayed-neutron energies. Average delayed-neutron energies of individual precursors were weighted by the corresponding delayed-neutron yields and combined to give average energies for all six delayed-neutron groups commonly used in reactor kinetics calculations

[en] Delayed-neutron emission probabilities (P/sub n/) were measured for 16 isotopes of Br, Rb, I, and Cs. Sources of chemically and mass separated nuclides were obtained from an on-line mass spectrometer facility. Neutrons were counted in a multitube polyethylene-moderated detector. The total number of precursor atoms was determined by direct counting of ions deposited on the first dynode of an electron multiplier. The P/sub n/ values from this work generally agree with earlier measurements for the longer-lived precursors but are consistently higher for the shorter-lived precursors. A log-log plot of P versus the reduced energy window (Q/sub β/ - B/sub n/)/(Q/sub β/ - C) gives a straight line with a slope of 6.0 +- 1.4, in agreement with simplified theoretical predictions. Half-lives of Rb and Cs nuclides measured by neutron decay curves are given

[en] Energy spectra of delayed neutrons from the precursors /sup 93,94,95/Rb and /sup 143/Cs have been measured by use of an on-line mass spectrometer and a /sup 3/He neutron spectrometer. Details of the experimental techniques, data analysis, and error estimates are given. A comparison of delayed-neutron spectra for /sup 87/Br, /sup 93,94,95/Rb, and /sup 143/Cs measured by three different laboratories is presented. Peak structures are reproduced by all laboratories, but the relative intensities below 200 keV vary according to different mesurement or data analysis techniques. 20 refs

[en] Fission product nuclides of Sr and Ba have been separated from their Rb and Cs isobars in an on-line spectrometer by the use of molecular fluoride ions of Ba and Sr formed on a hot Re surface. (Auth.)

[en] The β and subsequent γ decays of ⁹⁰Rb/sup g/ and ⁹⁰Rb/sup m/ have been studied using an on-line isotope separator system. Ge(Li) γ-ray singles and γ-γ coincidence measurements were used to construct level schemes for ⁹⁰Sr. The decays of the two ⁹⁰Rb activities were distinguished using a set of four experiments in which the collection and observation parameters were adjusted to change the relative decay intensities. For the decay of ⁹⁰Rb/sup g/, 83 attributed γ-ray transitions were placed among 33 excited states of ⁹⁰Sr, whereas for the decay of ⁹⁰Rb/sup m/, 43 excited states of ⁹⁰Sr provided placement for 108 attributed γ rays. Twelve γ rays were not placed in either level scheme, and 42 transitions are common to both decays. Spin and parity assignments have been deduced using β-decay logft values, γ-γ angular correlation data, and reaction data in the literature. Interpretation of some of the energy levels is made from a shell-model viewpoint

[en] Angular correlation measurements were made on 12 direct cascades and 5 skip cascades in ¹⁴⁰Ba. Levels in ¹⁴⁰Ba were populated from the 64-sec β decay of ¹⁴⁰Cs, which was populated from the decay of ¹⁴⁰Xe. The fission-product ¹⁴⁰Xe activity was produced by the TRISTAN isotope separator system. The most intense transitions were measured in coincidence with the first-excited state-to-ground-state transition in even-even ¹⁴⁰Ba. Definite spin assignments were made for eight levels and tentative spin assignments for five levels. Values are given for the angular correlation coefficients, and multipolarity mixing ratios are listed where applicable. Systematics for N=84 isotones are discussed in light of assignments made for ¹⁴⁰Ba

[en] Delayed neutron emission probabilities have been determined for Rb and Cs fission fragments by γ-spectroscopy of the precursors and their daughters. Sources were deposited on a movable tape by the SOLAR on-line mass spectrometer and viewed by a Ge(Li) detector. The γ spectra were multiscaled. Results are compared with those from counting neutrons per ion or β. (author)

[en] Angular-correlation measurements were made on ten direct cascades and four skip cascades in ⁹⁴Sr and on nine direct cascades in ⁹⁶Sr. These nuclei were populated by beta decay of isotopically pure ⁹⁴Rb and ⁹⁶Rb ion beams produced by fission and on-line mass separation. Correlations were measured for most of the intense transitions in coincidence with the 2⁺ → 0⁺ ground-state transition in both nuclei and two additional transitions in ⁹⁴Sr. Five levels in ⁹⁴Sr are given definite spin assignments and four levels tentative assignments. In ⁹⁶Sr definite spin assignments are made for four levels and tentative assignments for five levels. Values are listed for angular-correlation coefficients and, where applicable, multipole mixing ratios. Level systematics of neutron-rich even mass Sr isotopes are discussed within the context of assignments made here

[en] The damped collision sup(nat)U+₂₀₈Pb was investigated with the gas jet transport system at the Darmstadt UNILAC yielding very complex α-spectra. Utilizing a time-of-flight mass spectrometer for α-recoils many reaction products are identified by α-energies, α-ß coincidences and α-recoil masses. Most of the detected nuclides belong to the translead region. Some products with mass numbers around 150 are assigned to rare earth nuclides, which were produced in background reactions of the Pb ions in the Ti window foil or in the Ar thermalization gas. With 30% gas jet yield and 2% detector efficiency the overall efficiency of the system was 0.6%. (orig.)