The first excited states of 9Be and 9B
V.D. Efros1 - J.M. Bang2
1 Russian Research Centre "Kurchatov Institute", Kurchatov Square 1, 123182
2 The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
Received: 23 March 1998 / Revised version: 3 September 1998 Communicated by P. Schuck
It is found here that the 1/2+ first excited state of 9Be is a virtual state with the energy of -23.5 KeV. The line shape for the excitation of the state is approximated with a simple analytic form based on the effective range expansion. The partner in 9B of this state is found to be a resonance with a maximum in the peak at about 1.1 MeV, FWHM of 1.5 MeV, and complex energy of 0.6-i0.75 MeV. The line shape for its excitation is calculated in terms of the p-8Be phase shift. The phase shifts are obtained from N-8Be effective potentials deduced from the data on the photodisintegration of 9Be. A possibility for direct extraction of the energy of the resonant state from experimental data is also discussed, and an expression for a residue at a virtual state pole in terms of a quadrature taken over the virtual state eigenfunction is given.
21.10.Pc single-particle levels and strength functions - 23.50.+z Decay by proton emission - 24.30.Gd Other resonances - 27.20.+n - 03.65.Nk Nonrelativistic scattering theory