Elastic Scattering of Alpha Particles byO18

Abstract

The differential elastic scattering cross section of alpha particles by O 18 has been measured for alphaparticle energies between 2.4 and 3.5 MeV and for 0 c . m . =90. 0°, 125.3°, 140.7°, 152.3°, and 164.4° in order to determine the level parameters of excited states in Ne 22 . The resonances were analyzed using the singlelevel and two-level approximation to determine reduced widths and resonance energies of the levels. Scattering anomalies were observed at bombarding alpha-particle energies of 2.48, 2.56, 2.72, 2.90, 3.17, and 3.33 MeV which correspond to excited states of Ne 22 with the following energies, angular momenta, and parities: 11.70 MeV, /* = 2+; 11.76 MeV, /*=1-; 11.89 MeV, /*=1-; 12.04 MeV, /* = 0+; 12.26 MeV, J* = Q + ; 12.39 MeV, 7 7r = 2 + . For bombarding alpha-particle energies in the vicinity of 3.5 MeV, it was found necessary to include the effects of two levels above 3.5 MeV to fit the scattering data: 12.57 MeV, /*=1~ and 12.61 MeV, J v~\~~. None of the levels observed have reduced widths greater than 9% of the Wigner limit.

Investigation of theα-cluster structure ofNe22andGoldberg1, Rogachev2, Trzaska3 et al. 2004Phys. Rev. C522230View full textAdd to dashboardCite

“…The final identification was made by their detailed angular behavior and by the phase of the best fit. The resonance parameters agree with previous work [19,20]. The resonance at 12.80 is close to the minimum of the strong 1 − (12.82 MeV) state.…”

“…The anomaly at 180°corresponds to a stronger resonance than reported in Ref. [19,20]. However, the precision of the parameter determination is not certain due to the very high sensitivity of the calculations to the beam energy spread in the gas.…”

“…The influence of the lower-energy resonances on the parameters of the 11.88 MeV resonance was checked. Inclusion of the closest strong 1 − resonance at 11.76 MeV [19,20] has only a minor effect.…”

“…[18]. The present work concentrates on a detailed comparison of data in the region a few MeV above the ␣ decay threshold in 22 Ne with existing data obtained by conventional methods [19,20]. It is well known that ␣ capture by 18 O plays an important role in astrophysics [21].…”

“…They are rather close to each other so a formula for two interfering levels with the same spin and parity might be appropriate here. A corresponding analysis [19] showed only small differences in comparison with the simple expression (1); the correction can be taken into consideration by means of small changes of the phase shifts of these resonances using expression (1). Relatively small anomalies at 12.39 and 12.61 MeV can be followed practically throughout the total angular interval of these measurements.…”