  It has been shown in the past that in a shell model calculation, restricted
to 1Hbar*Omega 1p-1h configurations, the energy splitting between the lowest
J=0-, T=0 and J=0-, T=1 states in 16O is mainly due to the tensor component of
the nucleon-nucleon interaction. In this work, we extend the calculation to
include 3Hbar*Omega 2p-2h and 3p-3h configurations. We use realistic G matrices
derived from various One-Boson-Exchange potentials taking into account the
effects of the Dirac-Brueckner-Hartree-Fock approach, i.e., a modification of
the Dirac spinors for the nucleons in the medium. It is found that the
splitting is rather sensitive to the long-range components of the isovector
tensor force. The splitting is reduced considerably by including 2p-2h
configurations, in particular.
