T. Holtebekk

Resonance energies and half-widths for proton capture in aluminium

Abstract A description is given of the methods used to obtain precise values for the resonance energies and half-widths in proton capture reactions. A target chamber designed for this purpose is described. Proton capture in Al 27 has been investigated in the proton energy range 500 keV to 1400 keV. For all known resonances energy values are given. For some of the resonances the true half-widths and for the rest upper half-width limits are given.

Angular distributions of protons near resonance for the reaction 12C(d, pγ)13C obtained by shape studies of γ-ray lines

Abstract Angular distributions of protons from the reaction 12 C(d,pγ) 13 C have been obtained from the shape of the Doppler-shifted γ-ray lines. In particular, the 7 keV wide resonance at 1449 keV deuteron energy is studied. The distributions as a function of deuteron energy show interference effects which can be explained only by contributions from at least 4 other resonances, or from a direct reaction. The interference is clearly demonstrated by expressing the angular distributions in terms of Legendre polynomials, and studying the different terms in the distributions as functions of beam energy.

Resonance energies and half-widths for proton capture in sodium and phosphorus

Abstract The gamma ray yield from proton induced reactions in sodium and phosphorus has been studied in the proton energy range between 0.7 and 1.5 MeV for sodium, and in the energy range between 0.8 and 1.6 MeV for phosphorus. One new resonance in 31P at 1395.8±0.7keV is found. Relative determinations of the resonance energies are made with an accuracy of 0.05–0.1%. For 13 of the resonances in sodium and one of the resonances in phosphorus the half widths are determined. For the rest of the resonances upper limits for the half-widths between 200 eV and 750 eV are determined.

Beams of different masses in electrostatic accelerators

Abstract The use of the H2+ beam to obtain yield curves for (p, γ) reactions is shown to introduce an additional energy spread of about 0.5 keV at 500 keV proton energy. A simple explanation for this effect is suggested. We also find that the use of the H2+ beam leads to lower values for the resonance energies. Resonance energies and upper limits for the half-widths are given for three resonances in the Al27 (p, γ) Si28 reaction.

Angular distributions of protons from the reaction 12C(d, pγ)13C obtained by shape studies of γ-ray lines

Abstract A detailed study of the angular distributions of the emitted protons from the reaction 12C(d, p1)13C in the deuteron energy range 1.4 to 3.2 MeV is presented. The angular distributions are obtained from the line shape of the Doppler shifted γ-rays. The excitation function for the reaction shows strong intensity fluctuations which are superimposed on an energy dependent average behaviour. The reaction is therefore assumed to proceed through direct interaction as well as compound nucleus formation, and the amplitudes for the two different reaction mechanisms are added linearly to form the total reaction amplitude. The 14N resonance structure obtained is also based upon studies of the reactions (d, p2γ) and (d, p3γ).

Gamma-ray transitions in 20F from the reaction 19F(d, pγ)20F

Abstract Single γ-ray spectra and proton-gamma coincidence spectra from the reaction 19F(d, pγ)20F have been investigated with a Ge(Li) spectrometer. Precise excitation energies have been determined for levels up to 4083 keV. New information is obtained on the decay of the 3176 and 4083 keV levels.

RESONANCES FOR PROTON CAPTURE IN MAGNESIUM

Abstract The yield of beta-rays and gamma-rays from magnesium targets of natural isotopic composition has been measured in the proton energy range of 490 keV to 1390 keV, with special emphasis on the region 490 keV to 670 keV. Thirteen new resonances are reported. For some resonances the absolute yield of beta-rays per incoming proton is given. Resonance energies and upper limits for the half-widths are given for a number of resonances.

Mean lives of excited states in 28Al

Abstract The mean lives of excited states in 28Al formed in the 27Al(d,p) reaction have been determined from the measured Doppler shift of γ-rays emitted in coincidence with the protons. The multipole order and maximum admixture of higher order γ-radiation are determined. In several cases the result leads to a definite assignment or strongly favoured assumptions for the spin value of the excited state. A total of 28 levels below 5.45 MeV excitation energy have been studied. Previously mean lives have been reported for twelve of these levels. The experimental results indicate that several closely spaced doublets may be explained as a s 1 2 neutron coupled to states in 27Al.

Lifetimes of excited states in 20F

Abstract The lifetimes of some levels in 20 F have been measured by the Doppler-shift attenuation method in the 19 F(d, p γ ) 20 F reaction. The energy of γ-rays in coincidence with protons of selected energy is determined with a Ge(Li) spectrometer. Two targets are utilized, and γ-rays emitted in forward and backward directions relative to the motion of the recoiling nucleus are recorded simultaneously in the same spectrometer to eliminate drift or instability effects. From the observed lifetimes the multipole order and the maximum admixture of higher order γ-radiation are determined. The values are compared with those deduced from p- γ angular correlation measurements. In several cases this leads to definite assignments or strongly favoured assumptions for the spin values.

Two closely spaced resonances in the reaction Al27 (p, γ) Si28

An already known resonance is shown to consist of two separate resonances with Ep = 504.5±0.2 keV and Ep = 506.5±0.2 keV. Gamma transitions from the lower of the two levels proceed mostly to the ground state, while the upper level decays predominantly to the first excited state.