The first excited states of 9Be and 9B
V.D. Efros1 - J.M. Bang2
1 Russian Research Centre "Kurchatov Institute", Kurchatov Square 1, 123182
Moscow, Russia
2 The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
Received: 23 March 1998 / Revised version: 3 September 1998 Communicated by P. Schuck
Abstract
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.
PACS
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
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