Direct measurements of total reaction cross sections (sigma R) have been performed in the energy range of 10-300 MeV/nucleon for heavy ion collisions. A decrease of sigma R with increasing energy was observed for a wide range of masses of the colliding systems. The data suggest that sigma R reaches a minimum located around 300 MeV/nucleon independently of the projectile target combination. A dependence of sigma R on mass asymmetry of the svstem is also demonstrated. Trends of sigma R in this energy range are well reproduced by the predictions of a simple microscopic model based on individual nucleon-nucleon collisions. Our data have been employed in this framework to derive a new semi-empirical parametrization of sigma R. Most of the experimental results in the intermediate and high energy range have been reproduced by this parametrization using a single energy-dependent parameter.

Targets of $^{12}\mathrm{C}$ and $^{27}\mathrm{Al}$ have been bombarded by 35 MeV/nucleon $^{20}\mathrm{Ne}$ ions. Inside a cone of \ifmmode\pm\else\textpm\fi{}10\ifmmode^\circ\else\textdegree\fi{} around the beam axis, outgoing protons and \ensuremath{\alpha} particles were detected by an arrangement of 18 scintillators in coincidence with particles of charge Z=5--11 emerging at 2\ifmmode^\circ\else\textdegree\fi{}. At this energy the identified reaction mechanisms differ significantly from the ones observed in the 10--15 MeV/nucleon region. Important energy transfer of around 50 MeV to the target-like residues is observed. For the coincident oxygen-\ensuremath{\alpha} events, in addition to the well-known sequential decay mechanism of the projectile, about 40% of the events are attributed to another mechanism producing oxygen ions narrowly peaked near the beam velocity. Among the other reaction channels, cases are present which can be interpreted in terms of sequential decay alone, as well as others where admixtures of different processes play a role.

Direct measurements of total reaction cross sections between 100 and 300 MeV/nucleon indicate that σR reaches a minimum around 300 MeV/nucleon corresponding to the maximum of the (surface) transparency effects in heavy ion collisions. Data are well reproduced by simple microscopic calculations and are in agreement with the new parametrization we proposed earlier.

Measurements of σR have been performed at 30 and 83 MeV/nucleon incident energy for 15 heavy-ion systems using the attenuation method. The data are compared with predictions of microscopic calculations and a semi-empirical formula is given for σR.

The first results of direct measurements of heavy-ion reaction cross sections, ${\ensuremath{\sigma}}_{R}$, with use of the beam attenuation method are reported. For the $^{12}\mathrm{C}$ + $^{12}\mathrm{C}$ system ${\ensuremath{\sigma}}_{R}$ was measured at three incident energies, 112, 360, and 996 MeV. The data show deviations from the geometrical reaction cross section and agree with recent theoretical predictions based on Glauber theory.

Coincidences between light particles (Z ⩽ 4) and heavy ions (A ⩾ 9) have been measured for the 20Ne + 12C reaction at Elab(20Ne) = 160 MeV. α, 16O events from the 12C(20Ne, α16O)12C reaction and α, 20Ne events from 12C(20Ne, α20Ne)8Be have been found. Energy distributions and angular correlations of these events are consistent with α-decay from the intermediate nuclei 20Ne and 24Mg formed by inelastic scattering and α-transfer in a first reaction step.

Measurements of yields of evaporation residues identified by mass and charge following the reactions 20Ne + 12C (66.5 MeV) and 16O + 16O (55 MeV) have been carried out using a time-of-flight ΔE + E technique. These data have been analysed together with other data for compound nuclei with masses < 32 and Ex < 50 MeV in the framework of the statistical model using new computer codes which predict isotope cross sections and angular and energy distributions. A good description of all data is obtained and the determination of the critical l-value in the compound nucleus is shown to be possible using only the relative yields of the evaporation residues.

Cross sections for the radiative capture and one nucleon emission reactions have been obtained by mass identification of reaction products at 0\ifmmode^\circ\else\textdegree\fi{} using thin targets for the systems $^{12}\mathrm{C}$ + $^{14}\mathrm{N}$ (70 and 59 MeV), $^{30}\mathrm{Si}$ + $^{14}\mathrm{N}$ (70 and 59 MeV) and $^{27}\mathrm{Al}$ + $^{14}\mathrm{N}$ (59 MeV). The cross sections for radiative capture are in all cases 500 nb. The measurement of the $^{30}\mathrm{Si}$ + $^{14}\mathrm{N}$ cross section is in disagreement with previous work performed using thick targets. This discrepancy is discussed.NUCLEAR REACTIONS $^{12}\mathrm{C}$ + $^{14}\mathrm{N}$ (70 and 59 MeV), $^{30}\mathrm{Si}$ + $^{14}\mathrm{N}$ (70 and 59 MeV), $^{27}\mathrm{Al}$ + $^{14}\mathrm{N}$ (59 MeV) upper limits radiative capture cross sections + estimate of one nucleon emission cross section for $^{30}\mathrm{Si}$ + $^{14}\mathrm{N}$ (70 MeV).

Complete identification of products of the reaction 20Ne (110 MeV) + 12C has been carried out using time of flight and Δ E - E measurements. Angular distributions of reaction products and energy spectra were obtained between laboratory angles of 3.7° and 17°. The evaporation residue cross-sectionwas measured to be 1 270 + 150 mb. Analysis of the data has been carried out using the Hauser-Feshbach angular momentum dependent formalism. Nuclear reactions 12C(20Ne, X) E = 110 MeV. Simultaneous identification in mass and charge. Measured yields, energy spectra and angular distributions for 6 < A < 32. Evaporation analysis.

2014 La mesure de la diffusion de 16O sur 12C a été faite dans une région angulaire limitée dans les directions avant et arrière à des énergies laboratoires de 16O de 80, 85, 91, 93, 95, 101 et 122 MeV.La fonction d'excitation du maximum de la distribution angulaire situé près de 156° (c.m.) a aussi été mesurée par pas de ~ 0,5 MeV entre 80 et 101 MeV (lab.).Les résultats ont été ajoutés à d'autres résultats existants et la gross structure de l'évolution de la diffusion avec l'énergie a été analysée en utilisant un modèle optique dont le rayon imaginaire croit avec l'énergie.Abstract.-Measurements of the scattering of 16O on 12C have been made over a limited angular range in the forward and backward hemispheres at laboratory (16O) energies of 80,85,91,93,95,101, 122 MeV.The excitation function of the maximum near 156° (c.m.) has also been measured in steps of ~ 0.5 MeV between 80 and 101 MeV (lab.).The data were combined with other existing measure- ments and the gross structure features analyzed using an optical model whose imaginary radius increases with energy.

L'emission de rayonnement XK resultant d'une reaction nucleaire permet d'identifier la nature des atomes formes. Une correlation entre les sections efficaces de production de rayonnement X et de reaction nucleaire est etablie. La section efficace de reaction (α, xn) et (α, xnp) a ete mesuree sur le 209Bi entre 40 et 100 MeV et les rayons X provenant des atomes Z, Z + 1 et Z + 2 ont ete identifies. La correlation entre les sections efficaces est certaine. Le rayonnement hypersatellite du Bi est observe avec un decalage de 900 ± 70 eV. Des calculs relativistes sont effectues ; ils prevoient 1 300 eV.

We have recorded and analyzed spectra of x rays following proton and $\ensuremath{\alpha}$-particle bombardment of heavy atoms. The normal $K$ x rays are accompanied by satellite peaks originating from nuclear reactions. The phenomenon is very intense in $\ensuremath{\alpha}$-induced reactions and it is correlated with $\ensuremath{\alpha},xn$ cross sections; in the case of proton bombardment the intensity of the phenomenon is surprisingly weak. It is presumed that the ionization is due to internal conversion of residual $\ensuremath{\gamma}$ rays.

The possibility of using high-energy ion beams for analytical purposes is explored. The most promising field is the identification of medium-weight elements by detection of K X-rays following alpha-particle and proton bombardment, where a sensitivity well bellow 1 ppm was predicted. In the case of heavy elements, interferences are possible because of competition of nuclear reactions. In the case of rare earths, the method is interference free, quantities of 0.1 mg/cm2 can be determined.

The reactions 46, 48, 50Ti(p, t) have been studied with 40 MeV protons. The angular distributions obtained were analysed using zero-range DWBA calculations. Spin and parity assignments are given for levels up to about 10 MeV. In particular the levels of 46Ti at 9.16 and 9.60 MeV could be the T = 2 analogs of the ground state and of the 0.44 MeV excited state in 46Sc. Shell-model calculations with MSDI have been carried out for 44Ti with a (1f72, 2p32) space. The calculated level scheme is compared to the results of other calculations and to the experimental data.

The (p, t) and (p, 3He) reactions on 35, 37Cl are used to study the mirror and analogue states in Cl and S isotopes. The T = 32 states are identified at 5.55, 6.95, 7.35 and 8.10 MeV in 33Cl and at 5.65 and 7.25 MeV in 35Cl. Angular distributions for the strong transitions are obtained and analysed using a zero-range DWBA theory. The ratio of (p, t) and (p, 3He) cross sections are within theoretical limits. Shell-model calculations in the model space (2 s12, 1 d32)n have been carried out with four sets of two-body interaction matrix elements and the resulting level schemes and relative peak cross sections for (p, t) and (p, 3He) reactions are compared with experiment. Possible deficiencies in the model are discussed.

Absolute differential cross sections for the 11B(p, α) reaction leading to the ground state of 8Be have been measured at Ep = 12, 20, 24 and 30 MeV. These results and previous results at Ep = 26.7 and 38 MeV have been compared with PWBA calculations taking into account direct mechanisms and their interference term. Two possibilities have been investigated: firstly, pick-up and heavy-particle pick-up, secondly, knock-out and heavy-particle pick-up. Both possibilities agree well with experimental results.

Eighteen levels in the nucleus 48Cr have been observed in the reaction 50Cr(p, t)48Cr. In particular, the first T = 1 state (at 5.88 ± 0.03) and the first T = 2 state (at 8.86 ± 0.03 MeV) have been identified. DWBA calculations have been performed and spin assignments deduced for most excited states.