Scattering of 65 MeV helium ions from O 16

Abstract

In the inelastic scattering of 65 MeV helium ions by O 16, the following levels of O 16 were excited: 6.134, 6.918, 7.118, 8.876, 9.850, 10.363, 11.083, 11.52, 12.02, 12.443+12.528 (unresolved), 12.968+13.101 (unresolved), 13.981 and 14.94 MeV. Angular distributions were obtained for the particle groups corresponding to nearly all these O 16 levels. The levels at 8.876, 11.083, 12.528, 12.968 and 13.981 are of unnatural parity (i.e., parity (−) J+1 ). At small angles the angular distributions of the 8.876 MeV 2 − level oscillates in phase with the elastic angular distribution as a negative parity level should, but at angles greater than 45°, it behaves more like a positive parity level. The T = 1 levels at 12.968 and 13.101 MeV were excited about as strongly as neighbouring T = 0 levels. All negative parity levels of the p −1(s, d) configuration were observed where not forbidden by selection rules or obscured by their great width. The 9.59 MeV 1 − level was not observed; this confirms that it is a level of three-particle excitation. The 3 − level at 6.134 MeV showed collective enhancement of its cross section.