The 15N(d, τ) 14C reaction and high-lying T = 1 states in mass-14 nuclei: A determination of [formula omitted] 1p [formula omitted] diagonal matrix elements

Abstract

Energy spectra up to E x = 20 MeV and angular distributions of τ-particles from the 15N(d, τ) 14C reaction have been measured at an incident energy of 52 MeV and have been analysed by the DWBA. Five strong l = 1 transitions to 1p proton hole states occur up to E x = 11.29 MeV, which is 3 MeV above the particle emission threshold. The absence of direct l = 0 and l = 2 transitions demonstrates that 15N is a good shell-model nucleus with respect to protons. The isobaric analogue 1p hole states in 14C and 14N are identified by a comparison with T = 1 states excited in the 15N(p, d) reaction. This implies the following assignments for 14C levels: J π = 2 + for the 8.32 MeV level; J π = 1 + for a new level at 11.29±0.04 MeV with a width of 150±50 keV; J π = (0, 1, 2) + for one of the 10.433 and 10.453 MeV levels. This state corresponds to the formerly unknown T = 1, T z = 0 isobaric analogue at 12.52 MeV in 14N. The J π = 0 + and 1 +, T = 1 states of mass 14 are rather pure 1p hole states, while the (2 +, 1) states are strongly mixed with (s, d) 2 configurations. The complete 1p −2 spectrum could be observed. Combined with neutron pick-up data the six diagonal matrix elements of the 1 p 1 2 −2 and the 1 p 1 2 −1 1 p 3 2 −1 interaction have been determined and compared to theoretical results. The eight multipole coefficients α κτ ( j 1 j 2) have been calculated by the use of the energy weighted sum rules. The 1 p 1 2 −1 1 p 3 2 −1 spectrum is nearly identical to one produced by a δ-force without exchange terms.