The 0 + states of 12 C are considered within the framework of the microscopic three-α-cluster model. The main attention is paid to accurate calculation of the width of the extremely narrow near-threshold 0 + 2 state which plays a key role in stellar nucleosynthesis. It is shown that the

The axes or cores of extensive air showers have been selected by observing in a cloud chamber cascade showers produced by a single high-energy (>5 x lo9 ev) electron or photon, and an upper limit of 5 m for the spread of such particles has been found. By placing trays of hodoscoped counters at various distances from this core selector it has been possible to determine the relation between density of ionizing particles and distance from the axis for showers of approximately 1 04-105 particles. T h e experimental arrangement and method of analysis used have certain advantages over those employed by other workers. I t is concluded that although the results of the present experiment and those of other workers are consistent with the Molikre structure function, not too much weight should be placed on this agreement.

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Properties of the lowest 0 + states of 12 C are calculated to study the role of three-body interactions in the α-cluster model. An additional short-range part of the local three-body potential is introduced to incorporate the effects beyond the α-cluster model. There is enough freedom in this potential to reproduce the experimental values of the ground-state and excited-state energies and the ground-state root-mean-square radius. The calculations reveal two principal choices of the two-body and three-body potentials. Firstly, one can adjust the potentials to obtain the width

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