Mb. Barbaro et al., Pairing Hamiltonian for one pair of identical nucleons bound in a potential well - art. no. 011302, PHYS REV C, 6401(1), 2001, pp. 1302
The problem of one pair of identical nucleons sitting in N single particle
levels of a potential well and interacting through the pairing force is tre
ated introducing even Grassmann variables. The eigenvectors are analyticall
y expressed solely in terms of these with coefficients fixed by the eigenva
lues and the single particle energies. When the latter are those of a harmo
nic oscillator well an accurate expression is derived for both the collecti
ve eigenvalue and for those trapped in between the single particle levels,
for any strength of the pairing interaction and any number of levels. Notab
ly the trapped solutions are labeled through an index upon which they depen
d parabolically.