Excitation functions for 89 Y [(a,3n); (a,4n); (a,p3n); (a,an); (a,a2n)] reactions were measured up to 50 MeV using stacked foil activation technique and HPGe gamma ray spectroscopy method. The experimental data were compared with calculations considering equilibrium as well as preequilibrium reactions according to the hybrid model of Blann (ALICE/90). For (a,xnyp) type of reactions, the precompound contributions are described by the model. There seems to be indications of direct inelastic scattering e¡ects in (a,axn) type of reactions. To the best of our knowledge, the excitation functions for (a,4n), (a,p3n), (a,an) and (a,a2n) reactions were measured for the ¢rst time.

Excitation functions of the reactions 107Ag[(α, n); (α, 2n); (α, αn); (α, α2n)] and,109Ag[(α, 2n); (α, 3n); (α, 4n); (α, α3n); (α, α4n)] were investigated up to 70 MeV by the stacked foil activation technique and Ge(Li) gamma-ray spectroscopy method. Since the natural silver used as the target has two odd mass stable isotopes of abundance 51.83% (107Ag) and 48.17% (109Ag), their activation in some cases gives the same residual nucleus through different reaction channels, but with very different Q values. In such cases, the individual reaction cross sections are separated with the help of the ratio of theoretical cross sections. The experimental cross sections were compared with the predictions of a pre-equilibrium hybrid model. The (α, xn) reactions are fairly well reproduced with initial exciton number n0 = 4(4p0h), whereas (α, αxn) reactions are underestimated in magnitude by a factor of five to six.

Alpha particle induced reactions on the target element holmium were investigated upto 70 MeV using stacked foil activation technique and Ge(Li) gamma ray spectroscopy methods. Excitation functions for the formation of reaction residues 168Tm, 167Tm, 166Tm and 165Tm from α-induced reactions on 165Ho were investigated for the first time in the energy range from 50-70 MeV. The measured cross sections were compared with theoretical calculations considering equilibrium as well as preequilibrium hybrid models of Blann. The high energy tails of the excitation functions show a substantial contribution from preequilibrium emission. A general agreement is observed between the experimental results and theoretical predictions with an initial excition configuration of n0 = 4(4p 0h).

Blisters formation on the surface of kapton film has been observed due to 50 MeV Li 3þ ion irradiation up to the fluence of 1.04 Â 10 14 ions/cm 2 at ambient temperature. This investigation provides a foundation for a quantitative evaluation of the FTIR results for thermally stable polymer on the chemical bond deterioration with irradiation fluences. The blistering mechanism is correlated with the internal gases (CO, H 2 ) released due to Li 3þ ion induced radiation damage. The Vicker's micro-hardness testing has been carried out to study the mechanical behavior of irradiated films at room temperature. It is observed that the true bulk hardness of the film was obtained at loads greater than 400 mN. The hardness of the film increases significantly as fluence increases.

Excitation functions have been measured for alpha-particle induced reactions on natural nickel leading to the production of 62 Zn, 61 Cu, 56,57 Ni and 56,58 Co radioisotopes up to 50 MeV by the activation method and gamma-ray spectrometry. Most of these radioisotopes are produced by one or two alpha-particle emissions and a few nucleon emissions. The excitation functions were compared with semi-classical models codes, like ALICE/90, which includes a shell corrected level density formulation and the COM-PLET, which takes into account angular momentum removal effects. In the case of multi-nucleon emission channels, ALICE/90 gives fairly good agreement. The COM-PLET code on the other hand, explains the α-particle emission channels in a more convincing manner.

Excitation functions of the reactions 185 Re [(α,n); (α,2n); (α,3n)] and 187 Re [(α,n); (α,2n); (α,3n); (α,4n)] were investigated up to 50 MeV using the stacked-foil activation technique and high-purity germanium γ -ray spectroscopy method. Since the natural rhenium used as a target has two odd-mass stable isotopes of abundance 37.4% ( 185 Re) and 62.6% ( 187 Re), their activation in some cases gives the same residual nucleus through different reaction channels, but with very different Q values. In such cases, the individual reaction cross sections are separated with the help of the ratio of theoretical cross sections. The experimental cross sections were compared with the theoretical predictions considering equilibrium as well as pre-equilibrium contributions using code ALICE/90. It was found that the initial exciton configuration n 0 = 4 (4p0h) appears to give a good fit to the experimental data. To the best of our knowledge, the excitation functions for 185 Re[(α,n); (α,2n); (α,3n)] and 187 Re[(α,3n); (α,4n)] reactions were measured for the first time.Résumé : Utilisant une méthode d'activation en feuille et des mesures HPGe des rayons γ , nous étudions les fonctions d'excitation des réactions 185 Re[(α,n) ; (α,2n) ; (α,3n)] et 187 Re[(α,n) ; (α,2n) ; (α,3n) ; (α,4n)] . Parce que le rhénium naturel utilisé comme cible a deux isotopes impairs stables de 37,4% ( 185 Re) et 62,6% ( 187 Re) d'abondance respectivement, leur activation dans certains cas donne le même noyau résiduel via des canaux de réaction différents, mais avec des valeurs de Q très différentes. Dans de tels cas, nous séparons les sections efficaces des réactions individuelles avec l'aide des rapports théoriques des sections efficaces. Les sections efficaces ont été comparées avec celle prédites expérimentalement dans le cas d'équilibre et de pré-équilibre en utilisant le code ALICE/90. Nous trouvons que la configuration initiale d'excitation n 0 = 4 (4p0h) semble mener à un bon accord avec l'expérience. Au mieux de notre connaissance, c'est la première fois que sont mesurées les fonctions d'excitation pour les réactions 185 Re[(α,n) ; (α,2n) ; (α,3n)] et 187 Re [(α,3n) ; (α,4n)].[Traduit par la Rédaction]

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