Spectroscopy of natural parity states in 20Ne via the 19F(p,α0) and 19F(p,απ)reactions at low energies

The 19F(p,α0)16O and 19F(p,απ)16O reactions can be fruitfully exploited to probe natural parity states above the proton emission threshold in the compound 20Ne nucleus. However, despite the relatively large number of data sets published in the literature, it is still not possible to draw a fully unambiguous picture of the spectroscopy of 20Ne, especially close to the proton emission threshold. To contribute to clarify these aspects, we have collected and reviewed all existing data sets of the 19F(p,α0)16O and 19F(p,απ)16O reactions to perform, for the first time, a comprehensive R-matrix fit including both reactions in the bombarding energy range Ep = 0:2–10 MeV. Our analysis clarifies several ambiguities present in the literature and affecting the spectroscopy of 20Ne and clearly demonstrates the importance of the 19F(p,απ) reaction to better constraint the spectroscopy parameters of the fit.

Relevance via decomposition

We report on progress and an unsolved problem in our attempt to obtain a clear rationale for relevance logic via semantic decomposition trees. Suitable decomposition rules, constrained by a natural parity condition, generate a set of directly acceptable formulae that contains all axioms of the well-known system R, is closed under substitution and conjunction, satisfies the letter-sharing condition, but is not closed under detachment. To extend it, a natural recursion is built into the procedure for constructing decomposition trees. The resulting set of acceptable formulae has many attractive features, but it remains an open question whether it continues to satisfy the crucial letter-sharing condition.

PURE α-208Pb STATES IN 212Po REVEALED BY THEIR ENHANCED E1 DECAYS: A NOVEL α CLUSTERING

Excited states in 212 Po have been populated by α transfer using the 208 Pb (18 O ,14 C ) reaction and studied with the Euroball γ multidetector array. Very enhanced E1 transitions have been revealed by very short lifetimes measured by the DSAM method, found in the [0.1-1.4] ps range. The emitting states, which have non-natural parity values, are the fingerprints of the "α-208 Pb " structure present in 212 Po . They are in the same excitation-energy range as the states issued from shell-model configurations.

ENHANCED E1 DECAYS MEASURED IN 212Po POPULATED BY α TRANSFER: A NOVEL MANIFESTATION OF α CLUSTERING

Excited states in 212 Po have been populated by α transfer using the 208 Pb (18 O ,14 C ) reaction and studied with the Euroball γ multidetector array. Very enhanced E1 transitions have been revealed by very short lifetimes measured by the DSAM method, found in the [0.1-1.4] ps range. The emitting states, which have non-natural parity values, are the fingerprints of the "α-208 Pb " structure present in 212 Po .