G. G. Jonsson

The disintegration of nuclei in violent heavy ion interactions at 55A MeV-110A MeV

High multiplicity12C induced reactions in Ag(Br) at energies between 55A MeV and 110A MeV have been selected and investigated event by event in nuclear emulsions. Only a fraction of these events can possibly be described in terms of a normal thermal spectator-participant mechanism. Several events exhibit a violent breakup into several light and medium-mass fragments.A strong suppression of projectile associated proton- and composite particle emission in the forward direction is found in comparison with inclusive spectra. A large part of the low energy protons originates from a very slow source, with a velocity comparable to that of the heaviest fragment. The parallel fraction of the c.m. energy in each event, which is governed by the more energetic protons, has a broad distribution with a mean value of 0.61 and thus shows no signals of collective production mechanisms.

Some (γ, 1p × n) reactions in118Sn at intermediate energies

Yield curves for the production of117gIn,117mIn,116m1In,115mIn,113mIn,111In,110hIn,110lIn,109In,108hIn and108lIn from enriches118Sn have been measured by the activation method in the energy region 75–800 MeV. The cross sections have been deduced and for117In,110In and108In isomeric cross section ratios have been determined. The experimental cross sections are compared to calculations with a cascade-evaporation model and to cross sections calculated with a semi-empirical formula. The isomeric ratios are compared to calculations based on the statistical formalism by Huizenga and Vandenbosch together with cascade-evaporation theory. The (γ, p) cross section and isomeric ratio are also compared to calculations based on a direct knock-out formalism.

Electro- and photoinduced spallation reactions on27Al and51V at intermediate energies

Cross sections for some electro- and photoinduced spallation reactions on27Al and51V have been measured in the energy region 130–580 MeV with the activation method. The cross sections per photon are compared to Monte-Carlo calculations based on a cascade-evaporation model. The electrodisintegration cross sections are compared to calculations based on the Dalitz formalism for virtual photon spectra.

Total cross section for inclusive electron scattering in the lowQ2 region

Absolute cross sections for inclusive electron scattering on H, D, Be, Al, and Si have been measured in the kinematical region 0.08 (GeV/c)2<Q2<1.0 (GeV/c)2 and 0.3 GeV<v<6.5 GeV. The measurements have been performed at incident energies of 3, 5, 6, and 7 GeV and at the fixed scattering angle of 10°. A careful treatment of radiative corrections due to elastic electron nucleus scattering, quasielastic and inelastic scattering on the bound nucleons has been applied to the measured cross sections.The comparison of the nuclear cross sections with the elementary ones leads to a value ofAeff<A with a rapid onset of this effect at small values of the scaling variablex′.

Pion photoproduction on197Au to ground and isomeric states in197Hg

The cross sections for the photoproduction ofπ− on197Au leading to the 1/2− ground and 13/2+ isomeric states in197Hg have been measured from threshold to 750 MeV by use of the activation method. A suitable chemical separation technique was developed and applied in this experiment. The individual cross sections and the isomeric ratio are compared to calculations based on the impulse approximation.

Isomeric ratios in photon-induced spallation reactions at intermediate energies

Available experimental isomeric cross-section ratios in photon-induced spallation reactions at intermediate energies are compiled. The experimental data are compared to calculations based on the statistical model formalism.

The cosmic ray boron and carbon isotopic composition measured in nuclear emulsions

A study is made of the isotopic composition of primary cosmic ray boron and carbon in the energy interval 135–390 MeV/n. The quotients11B/(10B +11B) = 0.61 ±0.12 and13C/(12C +13C) = 0.06 ±0.04, valid at the top of the atmosphere, are obtained from photometric measurements on tracks found in an Ilford G5 emulsion stack exposed to the radiation.

Some (γ, π−xn) reactions on197Au at intermediate energies

The yields for some (γ, π− xn)-reactions on197Au have been measured from threshold to 750 MeV by use of the activation method. The experimental mean cross sections are compared to results obtained from other experiments on similar reactions and to cascade-evaporation calculations.

On the reaction118Sn(γ,p)117in at intermediate energies

A refined analytical calculation of the (γ, p) cross section on118Sn in the energy region 150–750 MeV has been performed, taking into account the contributions of single pion photoproduction. The result is in good agreement with experimental data.