Even-odd imbalance

What then of the clouds of nuclei billowing out from the stellar furnace One notable feature is that nature seems to prefer even numbers to odd. Apart from light hydrogen (A = 1), which is indeed a very special case, nature clearly favours the even. Abundances thus feature a marked even-odd imbalance. For those nuclei with fewer than 20 protons, the most abundant isotopes contain the... 

Likewise, even nuclei (with even numbers of protons) have lower probability (cross-section) for neutron capture than odd nuclei, and this results in a greater abundance of the former. The even-odd imbalance is manifested once again. 

The s process builds up an abundance distribution with peaks at mass numbers (A = Z + N) 87,138 and 208 and pronounced even-odd imbalance. The main component of the s process is associated with thermal pulsations of stars in the asymptotic giant branch (1-3 Mq) which produce neutron densities between 10 and 10 cm (Fig. 5.6). 

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