J. Ryckebusch, V. Van der Sluys, K. Heyde, H. Holvoet, W. Van Nespen, M. Waroquier, M. Vanderhaeghen Nuclear Physics A 624 (4), 581-6221997A1Published while none of the authors were employed at the CMMDOI http://dx.doi.org/10.1016/S0375-9474(97)00385-0