A new interaction called PSDPFB has been derived in the full p–sd–pf model space allowing one jump with a ⁴He core to describe the 1 \hbar \omega intruder states in sd shell nuclei. This new interaction was tested by calculating the evolution of the negative parity states throughout the shell. A low-lying 0^- state in ⁴⁰Ca is predicted. The interaction was applied to obtain the N=18 and 20 isotones spectra. Results for the isotones ³²Si, ³⁴S and ³⁶Ar and those for ³⁴Si, ³⁶S and ³⁸Ar are presented and compared to experiment.

PACS numbers: 21.60.Cs, 21.10.–k, 27.30.+t, 27.40.+z