GENERATOR-COORDINATE METHOD CALCULATIONS OF NATURAL ORBITALS AND SINGLE-PARTICLE OCCUPATION NUMBERS IN HE-4, O-16 AND CA-40

Single-particle occupation numbers and natural orbitals in4He,16O and40Ca are calculated diagonalizing the one-body density matrix obtained in an approach within the generator coordinate method. Square-well and harmonic-oscillator construction potentials and Skyrme-like forces are used. The natural orbitals (single-particle wave functions) are presented in both coordinate and momentum spaces. Together with the nucleon momentum distribution n(k) they are compared with results of Hartree-Fock as well as of correlation methods and with available experimental data for n(k) in4He. The realistic high-momentum behaviour of n(k) and of the natural orbitals in the case of square-well construction potential shows that the nucleon-nucleon correlations at small distances are taken into account. It is pointed out that the correlations strongly affect the natural orbitals but not the occupation numbers. © 1990 Società Italiana di Fisica.