Precision mass measurements of very short-lived, neutron-rich Na isotopes using a radio-frequency spectrometer - art. no. 054311

Mass measurements of high precision have been performed on sodium isotopes out to Na-30 using a new technique of radio-frequency excitation of ion tra jectories in a homogeneous magnetic field. This method, especially suited t o very short-lived nuclides, has allowed us to significantly reduce the unc ertainty in mass of the most exotic Na isotopes: a relative error of 5 x 10 (-7) was achieved for Na-28 having a half-life of only 30.5 ms and 9 x 10(- 7) for the weakly produced Na-30. Verifying and minimizing binding energy u ncertainties in this region of the nuclear chart is important for clarifica tion of a long-standing problem concerning the strength of the N = 20 magic shell closure. These results are the fruit of the commissioning of the new experimental program MISTRAL.