α Emission in proton induced reactions

The continuous spectra of theα particles emitted in reactions induced by protons on⁹³Nb,¹⁰⁷Ag,¹¹⁸Sn,¹⁶⁵Ho,¹⁶⁹Tm have been measured at several energies ranging from 20 to 45 MeV. The spectra have been analysed in the framework of the Exciton model assuming that the emittedα's pre-existed in the target nucleus and evaluating their energy distribution on the basis of nucleon-α scattering dynamics in nuclear matter. Nuclear Reactions⁹³Nb,¹⁰⁷Ag,¹¹⁸Sn,¹⁶⁵Ho,¹⁶⁹Tm(p,α...).E=20–45MeV; Measured \(\frac{{d\sigma (E_\alpha )}}{{dE_\alpha }}\) ; calculated \(\frac{{d\sigma (E_\alpha )}}{{dE_\alpha }}\) .     

Excitation functions of evaporation residues in the interaction of 16O with 103Rh at incident energies up to 400 MeV

The excitation functions for production of 48 residues in the interaction of ¹⁶O with ¹⁰³Rh have been measured at incident energies varying from about 40 to 400MeV. Their analysis shows that many competing reaction mechanism contribute to the formation of these residues including complete fusion, break-up-fusion reactions and ¹⁶O inelastic scattering. The cross-sections of most of these mechanisms are obtained by independent measurements of the spectra of intermediate-mass fragments observed in the interaction of ¹⁶O on ⁹³Nb. The agreement between measured and calculated excitation functions is satisfactory in most of the cases.     

The mechanism of the (p, α) reaction: Pick-up or knock-out?

Several early studies of the (p, α) reaction to discrete states of the final nucleus indicated that it proceeds mainly by the pick-up mechanism, whereas more recent experiments provide qualitative arguments in favour of the knock-out mechanism. This paper reports calculations showing that the angular distributions and analysing powers of the^90,92Zr(p, α)^87,89Y and¹¹⁸Sn(p, α)¹¹⁵In reactions can be equally well fitted by distorted wave calculations using either mechanism.     

Nucleon mean free path in nuclear matter

In calculations of nuclear reaction yields at incident energies of some tens of MeV consistently better agreement with experiments is obtained by assuming a nucleon mean free path in nuclear matter longer than that deduced from the Fermi gas model and free nucleon-nucleon cross sections.     

Nuclear Thermalization

The thermalization of a composite nucleus formed when two heavy ion fuse, that is the transformation of the orderly translational motion energy of the two ions into chaotic, thermal motion energy may be described by a set of Boltzmann master equations which allow one to calculate the time evolution of the single nucleon energies within the composite nucleus. The theoretical assumptions and the results of the analysis of the experimental data are discussed.     

Evidence for a dissipative friction mechanism based on 8Be fragments from the interaction of 12C with 59Co

It is suggested that the spectra of the ⁸Be ground-state (gs) nuclei produced in the interaction of ¹²C with ⁵⁹Co at incident energies varying from 8.3 to 33.3 MeV/amu can be explained by introducing a dissipative friction interaction mechanism preceding projectile break-up. Received: 27 March 2000 / Accepted: 11 April 2000     

Excitation of single proton states in (p, α) reactions

A high resolution experiment, using the BIG KARL spectrometer has been made to identify the levels of ¹⁴¹ Pr excited in the ¹⁴⁴ Nd(p,α) reaction at 25 MeV. It has been found that only levels with a dominant single proton component are populated with appreciable intensity.     

Emission of alpha particles in the interaction of 10–85 MeV protons with48,50Ti

The excitation functions of twenty nuclear reactions induced by protons of up to 85 MeV incident upon⁴⁸Ti and⁵⁰Ti targets have been measured. Most of these involve the emission of one to three alpha particles. The Exciton model has been used to calculate these excitation functions. An expanded and more precise treatment of nucleon-alpha scattering has been incorporated into the model. It is presented and the implications of its predictions discussed. The agreement of experiment and calculation is very good lending support to the approach to alpha particle interactions introduced in this work.     

Absorption of stopped π− in 59Co, 75As, 197Au and 209Bi investigated by in-beam and activation γ-ray spectroscopy

In-beam pionic X-ray and γ-ray spectra and activation γ-ray spectra following π^? absorption at rest in ⁵⁹Co, ⁷⁵As, ¹⁹⁷Au and ²⁰⁹Bi have been measured. The isotopic yield distributions and thus the (π^?, xnγp) reaction yields were determined. The mean numbers of emitted neutrons and protons are, respectively, 4.5 ± 0.2 and 1.48 ± 0.16 for ⁵⁹Co, 5.1 ± 0.3 and 1.02 ± 0.14 for ⁷⁵As, 6.6 ± 0.4 and 0.32 ± 0.14 for ¹⁹⁷Au, and 6.8 ± 0.4 and 0.37 ± 0.16 for ²⁰⁹Bi. The experimental results are compared with a pre-equilibrium exciton model calculation and proton-induced spallation reactions. High spin states in the residual nuclei were observed. For pionic X-rays absolute intensities of various transitions are given.