Number conserving shell model for even Ca, Ti, Cr, and Fe isotopes

The nuclear properties of the low lying states of even isotopes of Ca, Ti, Cr, and Fe are calculated in the framework of the broken pair approximation. The broken pair approximation configuration space for an even number of identical valence nucleons includes all the seniority (ν) two components while for nonidentical (even-even) valence nucleons, it contains all configurations with ν< or =4 except ν = 4 proton components and ν = 4 neutron components. The calculations have been carried out with a 40Ca core using two different sets of realistic interaction matrix elements: (i) The set reported by Kuo and Brown and its modified version due to McGrory; (ii) A set of Tabakin interaction matrix elements which includes the second order Born term and core polarization effects. The effect of the truncation of the valence space has been examined in detail. The calculated energy spectra, quadrupole moments for the first 2+ states and E2 transition rates, compare well with the corresponding shell model results (wherever available) as well as with the experiment