Published in:Jülich : Kernforschungsanlage Jülich, Verlag, Berichte der Kernforschungsanlage Jülich 993, VI, 38 p. (1976).
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English
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Description:
In this report a compilation of measured differential cross sections for elastic and inelastic scattering of protons on $^{12}$C in the energy range from 22.5 to 45 MeV is given. The aim of these measurements was to get in small energy intervals systematic and consistent data about the energy dependence of the puzzling back angle structure in the differential cross sections especially for inelastic scattering to unnatural spin parity states (e.g. 1$^{+}$ , 2$^{-}$ , 3$^{+}$ . ) . This compilation gives the exact data on which the following paper is based: Investigation of giant resonances as doorway states in inelastic nucleon scattering from $^{12}$C H.V. Geramb, K. Arnos, R. Sprickmann, K.T. Knöpfle, M. Rogge, D. Ingham, C. Mayer-Böricke Physical Review C, Vol. 12, No. 6 (1975) 1697. From these data, information about gross structures of giant multipole resonances for $\lambda$ = 1 to 4 can be obtained from a microscopic DW analysis$^{1-5)}$. According to the special features of this theory, the experiments concentrated mainly on the transitions to the unnatural parity states at E$_{x}$ = 12.71 MeV (T=O) and E$_{x}$ = 15.11 MeV (T=1) with spin 1$^{+}$. The measurements were performed at the Jülich Isochronous Cyclotron JULIC at 12 incident proton energies: 22.5, 24 to 40 MeV in 2 MeV steps, 42.5 and 45 MeV. Spectra were taken with $\Delta$E-E counter telescopes consisting of 0.1 to 1 mm thick standard surface barrier $\Delta$E counters and 24 mm long Ge(Li) diodes as E counters$^{6)}$. The counter efficiencies were checked by re-measuring anoular distributions at 22.5 and 24 MeV with a telescooe with a 2 mm thick surface barrier E detector. The data are corrected for pile-up and ADC dead time effects. The measured angular distributions extend over the range 20° (30°) $\le$ A$_{Lab}$ $\le$ 160° in 5° steps; this angular range was sometimes restricted for the weaker transitions in the forward region. Figure 1 gives a level scheme of $^{12}$C, where all states up to an excitation energy of about 16.5 MeV are ...