We use a large-scale 6h Omega calculation for Li-6 with microscopicall
y derived two-body interaction to construct the 0h Omega 0p shell effe
ctive Hamiltonian, electric quadrupole, and magnetic dipole operators.
While the E2 and M1 6h Omega operators are one-body operators with fr
ee nucleon charges, the effective operators are two-body operators wit
h substantially different renormalization for the isoscalar and isovec
tor matrix elements, especially for the E2 operator. We show that thes
e operators can be very well approximated by one-body operators provid
ed that effective proton and neutron charges are used. The obtained ef
fective charges are compatible with those used in phenomenological she
ll-model studies. The two-body part of the effective operators is esti
mated.