HOW TO COUNT NUCLEON PAIRS

Within the context of the isovector-pairing SO(5) model, three methods measuring numbers of different kinds of nucleon pairs are discussed. Though methods do not give the same results, the odd-even staggering i n pair numbers in even-even and odd-odd N=Z nuclei and the reduction o f the np-pair number with increasing T-z is observed in all three proc edures. (C) 1997 Elsevier Science B.V.