0000000000073924
AUTHOR
P. Peuser
The new neutron-rich isotope183Lu
The new neutron-rich isotope183Lu was produced in multinucleon transfer reactions by irradiatingnatW/Ta targets with 11.7 MeV/u136Xe ions, and identified by mass separation and decay spectroscopy. The measured half-life of183Lu is 58±4 s. The properties of the excited states of183Hf are discussed.
Sensitive laser spectroscopy on trapped barium ions by quenching with hydrogen
The sensitivity of laser spectroscopy on barium ions stored in a radio frequency quadrupole trap was drastically increased by using hydrogen for quenching the optically pumped metastable states. The attained fluorescence intensity per ion permits the detection of single ions. The method will be applied to environmental studies on actinides.
Laser resonant ionization of plutonium
Resonance ionization mass spectrometry (RIMS) has been tested for the isotope-selective determination of trace amounts of plutonium. An atomic beam is formed by evaporating plutonium atoms from a rhenium-filament heated to 1800 °C. The radiation of a pulsed dye laser excites the atoms in a two-photon process (λ=595.2 nm) followed by photoionization of the excited atoms. Mass selectivity is obtained by use of a time-of-flight spectrometer. A resonant signal of239Pu was measured with 1013 atoms deposited on the filament.
Search for Superheavy Elements in theU238+U238Reaction
A search was made for spontaneously fissioning superheavy elements in damped collisions of two uranium nuclei. Different techniques were applied covering the elements 108 to 118 and approx. =126, and a half-life range from 1 ms to more than 1 yr. No evidence for superheavy elements was found at upper cross-section limits of 10/sup -32/, 10/sup -33/, and 10/sup -35/ cm/sup 2/ for half-lives from 1 to 100 ms, 100 ms to 1 d, and 1 d to 1 yr, respectively.
Half-lives, neutron emission probabilities and fission yields of neutron-rich rubidium isotopes in the mass regionA=96 toA=100
Neutron-rich rubidium isotopes were produced by thermal-neutron induced fission of235U and were isolated by surface ionization and mass separation. The new isotope (51 ±17) ms100Rb was identified. The half-lives of the rubidium isotopes with mass numberA=96 toA=100 were measured using neutron multiscaling or gamma multispectrum analysis. Measurements of the delayed-neutron emission probabilityP n of99Rb and of the fission yields of97Rb,98Rb, and99Rb were performed.
Trace detection of plutonium by three-step photoionization with a laser system pumped by a copper vapor laser
Laser photoionization has been used to detect trace amounts of plutonium. A high sensitivity and selectivity has been achieved by applying three-step excitation and ionization of the plutonium atoms with high pulse-repetition rates and additional mass determination by time-of-flight measurements. A laser system was developed which consists of a copper vapor laser pumping three dye lasers simultaneously. Samples containing between 1010 and 1012 atoms of239Pu on Re filaments were measured yielding strong resonance signals with maximum ion count rates of several kHz at a vanishingly low background. A detection efficiency of 10−7 was determined allowing the detection of about 108 plutonium atom…
Beta-delayed neutron emission from93?100Rb to excited states in the residual Sr isotopes
Beta-delayed neutron emission from the precursors93–100Rb to excited states in the residual nuclei92–99Sr has been measured by means ofγ-ray and neutron spectroscopy. In general, considerable neutron feeding of excited final states is observed. The experimental branching ratios (P ) are compared to predictions from statistical model calculations. It is demonstrated that the main parameter affecting theP -values is the shape of theβ-strength function (S β). For several Rb isotopes hindrance, respectively enhancement of neutron branches to specific final states is observed giving evidence for the persistence of intermediate structure of the neutron-emitting states. By the example of98Rb it is…
Search for superheavy elements in damped collisions betweenU238andCm248
Negative results for the production of superheavy elements in damped collisions between $^{238}\mathrm{U}$ projectiles and $^{248}\mathrm{Cm}$ targets are reported. This reaction was believed to permit a closer and more widespread approach to the predicted island of stability near Z=114 and N=184 than any practical fusion reaction. Aqueous and gas phase chemistry techniques were used to isolate superheavy element fractions. The fractions were counted for spontaneous fission activity, fragment kinetic energies, and neutron multiplicities. Cross-section limits for half-lives from hours to several years are g4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}35}$ ${\mathrm{cm}}^{…
Levels in104Ru populated by the ??-decay of104Tc
Theβ− — andγ-activities of 18.4 min104Tc have been studied with singles and coincidence measurements. Sources were prepared by chemical separation of technetium from the fission products of thermal-neutron-induced fission of235U. A revised level scheme of104Ru up to an excitation energy of 4.26 MeV is proposed. Fromβ-γ coincidence measurements, aQβ-value of 5.62±0.07 MeV has been obtained.
Determination of Qβ values from endpoint energies of beta spectra
Abstract A plastic scintillator telescope is described for determining beta endpoint energies up to 15 MeV. The response function of the telescope was measured using monoenergetic electrons from a betatron. A nonlinear procedure for unfolding the measured beta spectra on the basis of the experimental response function was tested successfully.
Search for long-lived superheavy elements in the reaction of136Xe with238U
A search with radiochemical methods for long-lived superheavy elements in 238U targets bombarded with intense beams of136Xe ions produced negative results. A formation cross section of ≤1×10−35 cm2 is deduced at 95% confidence level for nuclides with half-lives between 1 and 200 d.