Charge-independent trend of isoscalar matrix elements along the N∼Z line

Shell model calculations have been carried out using the m-scheme numerical code ANTOINE in order to elucidate the particular trend of the isoscalar matrix elements, M0, for A=4n+2 isobaric triplets ranging from A=18 to A=42. The transition energies, reduced transition probabilities and isoscalar matrix elements are predicted to a high degree of accuracy. The general agreement of M0 between those from mirror pairs and those from TZ=0 nuclides support our shell model calculations. The predicted results tie together recent experimental data, and the trend of M0 strength along the sd and beginning of the fp shells is interpreted in terms of the dynamic shell structure. Certain discrepancies arise at A=18 and A=38 isobaric triplets, which might be explained in terms of core polarization effects and the low occupancy of the orbits at the extremes of the sd shell.