J. Dubois

Virtual levels in the vanadium isotopes from proton bombardment of the titanium isotopes

Electromagnetically separated Ti-isotopes were bombarded by protons in the 800 to 1400 kev interval. From the (p, gamma ) resonances the virtual levels in the V-isotopes were determined. Revels spacings are discussed. (auth)

Application of an Energy Dispersive X-Ray Fluorescence Spectrometer to Air Pollution Studies

A secondary target Energy Dispersive X-ray Fluorescence spectrometer with three axial geometry has been used in multielement analysis of aerosols. A new type of monitoring system has been designed to monitor the flow of secondary photons and thus minimize the influence of time variation in the X-ray intensity. The aerosols were divided in two size fractions by means of a virtual impactor and deposited on filters. The absolute concentrations of the different elements were obtained by use of standard samples with known element concentrations. Detection limits for sixteen elements are given and are in the order of ng per cm2. The method has been applied to aerosols of widely varying composition and concentration in ambient atmosphere and industrial environment.

On the branching ratios of the lowest Jπ = 12+ stats in the mirror nuclei 23Na and 23Mg

Abstract The branching ratio of the electromagnetic decay of the J π = 1 2 + level at 2.393 MeV in 23 Na has been determined from a study of the 22 Ne( 3 He, dγ) 23 Na reaction using particle-gamma coincidence technique. Theoretical calculations using the collective model and including isospin as a good quantum number seem to account for the experimental result as well as the vastly different branching ratio for the corresponding level in 23 Mg.

Half-lives of the positon emitting mirror nucleides

Abstract The half-lives of the positon emitters C11 N13 F17 Na21 Al25 and A188, P80 have been determined. The decay spectrum of Al25 has been investigated. No evidence for γ-rays indicating a complex decay was found. A plot of log T 1 2 against log A 2 3 is discussed in terms of shell effects. It is shown that individual lines can be drawn through the points belonging to successive proton subshells. The value for Ne19 falls below the line representing the d 5 2 subshell, which somewhat favours the proposal that the ground states of Ne19 and F19 are 2 s 1 2 -states From a plot of the β+-energies the pairing energy difference seems to have a value of about 0.1 MeV in the d 5 1 -subshell.

The 34S(3He, αγ)33S reaction and the lowest T = 32 states in 33S

Abstract Energy levels up to 7.5 MeV in 33 S have been investigated by means of magnetic analysis of the alpha particles from the 34 S( 3 He, αγ) 33 S reaction at 7 and 12 MeV bombarding energies. Angular distributions were measured, and the angular momenta transferred by the picked-up neutrons were determined from optical-model analysis using DWBA. The hole state created by picking up a neutron from the 1 d 3 4 orbit is suggested to be at 2870 ± 10 keV. The lowest T = 3 4 states in 33 S were found at 5479 ± 15, 6900 ± 20 keV. The gamma decay of the 5479 keV level was investigated.

New bound levels in 43Sc from radiative proton capture in 42Ca

Abstract With a lithium-drifted germanium solid state detector we have studied the gamma radiation from the 42Ca(p, γ)43Sc reaction at seven resonances. The excellent resolving power and the good linearity of the detector have made it possible to determine accurately the decay scheme of 43Sc. The levels found at 150±1, 472±1, 844±2, 877±2, 1175±4, 1649±7 and 2089±7 keV are in good agreement with our earlier results obtained with NaI crystals. Additional new levels have been found at 1959±7, 2137±7, 2200±7, 2587±10, 2676±10, 2979±10, 3297±10 and 3809±10 keV and new levels at 1150±10 and 2382±10 keV are suggested. The Q value of the reaction was determined to 4937±5 keV.

A Search for a Missing Jπ=3/2+ level in 21Na

The 20Ne(3He,d)21Na reaction has been studied at 16 MeV bombarding energy. The emitted deuterons have been analysed in a double focusing magnet. Levels in 21Na were deduced. Furthermore the 20Ne(p,γ)21Na reaction has been investigated using a 44 cm3 Ge(Li) detector. Gamma ray branching ratios and life times have been measured at the 1 169, 1 311 and 1 504 keV resonances. The experimental information is discussed in terms of the Nilsson strong-coupling model and recent shell model calculations.

Cross sections for 18O+9Be induced reactions at sub-coulomb energies

Abstract Cross sections for reactions induced by 18 O on 9 Be have been measured in the energy range E c . m . = 1.8 MeV to 6.7 MeV. The yields of characteristic γ-rays were observed with a Ge(Li) detector and absolute cross sections were deduced for formation of 19 O, 21, 22, 23 Ne, 24, 25 Na and 25 Mg. The 9 Be( 18 O, 19 O) 8 Be transfer cross section was found to dominate over the total fusion cross section below E c . m . = 4.5 MeV. The energy dependence of the measured transfer cross section agrees well with what is expected for a reaction of optimum Q -value at low incident energies.

STUDY OF LEVELS IN

A versatile facility for studying nuclear reaction has been built. The 20Ne-(d,pγ)21Ne reaction has been studied using particle-gamma and gamma-gamma coincidence technique. Surface barrier solid state detectors and Ge(Li)-detectors were used together with a multi-dimensional storage of data in a PDP-15 on-line computer. Energies and gamma radiation branching ratios of levels in 21Ne up to 4.7 MeV have been measured. Levels in 21Ne are discussed in terms of modern shell model calculations and the Nilsson strong-coupling model.

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The 22Ne(d,nγ)23Na reaction has been used to study the γ-ray deexcitation of 1/2+ levels in 23Na. New branches were found for the T = 3/2 level at 8.66 MeV. The experimental ΔT = 1, γ-ray transition strengths for this level cannot be explained by simple shell model theory but agree very well with those predicted by the collective model using Nilsson wavefunctions.