Resonance parameters of the first 1/2+ state in 9Be and astrophysical implications

TL;DR

This study measures the resonance parameters of the first 1/2+ state in 9Be using electron scattering, providing improved precision and discussing implications for astrophysical processes like 12C production.

Contribution

The paper presents high-resolution electron scattering measurements to accurately determine resonance parameters of 9Be's first excited state, with implications for astrophysics.

Findings

Resonance energy E_R = 1.748(6) MeV

Resonance width Gamma_R = 274(8) keV

Reduced B(E1) strength is half of previous estimates

Abstract

Spectra of the 9Be(e,e') reaction have been measured at the S-DALINAC at an electron energy E_0 = 73 MeV and scattering angles of 93{\deg} and 141{\deg} with high energy resolution up to excitation energies E_x = 8 MeV. The astrophysically relevant resonance parameters of the first excited 1/2+ state of 9Be have been extracted in a one-level approximation of R-matrix theory resulting in a resonance energy E_R = 1.748(6) MeV and width Gamma_R = 274(8) keV in good agreement with the latest 9Be(gamma,n) experiment but with considerably improved uncertainties. However, the reduced B(E1) transition strength deduced from an extrapolation of the (e,e') data to the photon point is a factor of two smaller. Implications of the new results for a possible production of 12C in neutron-rich astrophysical scenarios are discussed.