Excitation Function of $^{12}$C(p,po) for Ep=16 $\div$ 19.5 MeV measured by MSS with resolution ~10 keV

Abstract

The elastic scattering $^{12}$C(p,po) Excitation Function (EF) was measured in the energy range Ep =16 - 19.5 MeV with resolution about 10 keV by means of innovative approach - MSS - the Method of Spectra Superposition at the 14-angle Magnetic Spectrograph (Apelsin) at beam with an energy spread of about 200 keV from U-150 cyclotron of INP Ulugbek (Tashkent) of Science Academy of Uzbekistan [1-8]. The obtained EF has a reach structure of anomalies in precise agreement with thresholds and levels data [2,9-12]. Measurements were done on the 12C self-supporting target with thickness 13 mg/cm2 and an area of 1 cm2 in the center of Apelsin. The 20-step Energy Moderator controlled the proton energy, providing a 3.5 MeV wide Ep interval with no readjustment of cyclotron and all the ionic-optics on the 41-meter-long beam-pipe. Energy resolution of Apelsin for protons is better than 5 keV along all focal plane, where particle-product were detected by specially designed coordinate-sensitive gas mixture MWPC with two particle counters in coincidence. The acquisition system was based on IBM PC online with a fast CAMAC branch (custom designed at St-Petersburg PNPI) with fast TDC modules and other fast electronics providing immediate selection and accumulations of events from MWPCs. The NMR-monitor system stabilized spectrographs magnetic field to 3ppm [1,9]. The EF of 12C (p,po) scattering has many resonances that precisely correspond to g.s. and levels of well-known product-nuclei. But 80 percent of anomalies did not have any explanation. A new concept is proposed to explain all unrecognized anomalies. Two expressions Writing I and Writing II proposed to explain the unknown peaks which corresponds to population of A13 phase volume states. The results of the proposed explanation look very promising (Fig. 13). Concept of the Combinative Isobaric Resonances (CIRs) proposed