The effect of expansion of the shell model space on the structure of the mass-15 nuclei

The structure of the natural and unnatural parity states of the¹⁵N-¹⁵O mirror pair, as well as theT=3/2 analogue states of¹⁵C, is discussed in terms of shell model calculations with a modified surface delta two-body interaction. The inert core is recomposed from⁴He to¹²C and the configuration space is systematically expanded to allow for an increasing number of particle excitations from the 1p into the 2s-1d shell. The relative importance of the 2s 1/2, 1d 5/2 and 1d 3/2 orbitals are evaluated. Some electromagnetic properties of levels are also calculated.