We report a measurement of a new high spin J π = 5 − state at 22.4(0.2) MeV in 12 C which fits very well to the predicted (ground state) rotational band of an oblate equilateral triangular spinning top with a D 3h symmetry characterized by the sequence 0 + , 2 + , 3 − , 4 ± , 5 − with almost degenerate 4 + and 4 − (parity doublet) states. Such a D 3h symmetry was observed in triatomic molecules and it is observed here for the first time in nuclear physics. We discuss a classification of other rotation-vibration bands in 12 C such as the (0 + ) Hoyle band and the (1 − ) bending mode band and suggest measurements in search of the predicted ("missing") states that may shed new light on clustering in 12 C and light nuclei. In particular the observation (or non-observation) of the predicted ("missing") states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha-particle composing the Hoyle state at 7.654 MeV in 12 C.

The NEMO collaboration is looking to measure neutrinoless double beta decay. The search for the effective neutrino mass will approach a lower limit of 0.1 eV. The NEMO 3 detector is now operating in the Frejus Underground Laboratory. The fundamental design of the detector is reviewed and the performances detailed. Finally, a summary of the data collected in the first runs which involve energy and time calibration and study of the background are presented.

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The very neutron-rich oxygen isotopes 25