Ab initiocalculations of nuclear widths via an integral relation

Abstract

I describe the computation of energy widths of nuclear states using an integral over the interaction region of ab initio variational Monte Carlo wave functions, and I present calculated widths for many states. I begin by presenting relations that connect certain short-range integrals to widths. I then present predicted widths for 5 ≤ A ≤ 9 nuclei, and I compare them against measured widths. They match the data more closely and with less ambiguity than estimates based on spectroscopic factors. I consider the consequences of my results for identification of observed states in 8 B, 9 He, and 9 Li. I also examine failures of the method and conclude that they generally involve broad states and variational wave functions that are not strongly peaked in the interaction region. After examining bound-state overlap functions computed from a similar integral relation, I conclude that overlap calculations can diagnose cases in which computed widths should not be trusted.

Proton-decaying states in light nuclei and the first observation of Na17

“…[16]. Recent ab initio calculations with the Variational Monte Carlo method predict the width to be Γ = 102 ± 5 keV [17], which is consistent with the transfer work, but inconsistent with our measurement. However even more recent results from the Shell Model with the source-term approach (STA) predict a width of Γ ST A = 53 keV, which reproduces our result [18].…”

“…This work made use of two secondary beams produced by the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory at Michigan State University: 9 C (E/A = 68 MeV, intensity = 5.0 × 10 4 pps, 52% purity) produced from a 16 O primary beam (E/A = 150 MeV, 175 pnA) and 17 Ne (E/A = 58 MeV, intensity = 1.6 × 10 4 pps, 11% purity, where the largest component of the total intensity of 1.5 × 10 5 was 15 O) from a 20 Ne primary beam (E/A = 170 MeV, 80 pnA). The details of these experiments have been published elsewhere [1,3].…”

“…We are also able to populate 2-proton decaying excited states in 17 Ne through inelastic excitation of the 17 Ne beam. The continuum states of 17 Ne up to E * = 6.5 MeV were studied almost 20 years ago through the 20 Ne( 3 He, 6 He) 17 Ne reaction [29].…”

“…States in 17 Na can be populated with a 17 Ne beam either by charge-exchange reactions with the target or through more complicated reactions. Prior to this work it was known that 17 Na was unbound but its continuum structure was unexplored.…”

“…For two-proton decaying states, this method can also determine whether the decay occurs directly or by two sequential one-proton decays through an intermediate nucleus by measuring the energy and angular correlations between the decay fragments. In this paper we present new information on the excited states of the proton-rich nuclei 8 B, 9 B, 9 C, 16 F, and 17 Ne, and the first observation of the proton unbound nucleus 17 Na.…”