arXiv subjects

L. Lamia

Publications and source records attributed to L. Lamia.

23 records · Page 2Linked to original sources

arXiv2012

Trojan Horse method and radioactive ion beams: study of $^{18}$F(p,$α$)$^{15}$O reaction at astrophysical energies

The Trojan Horse Method was applied for the first time to a Radioactive Ion Beam induced reaction to study the reaction $^{18}$F(p,$α$)$^{15}$O via the three body reaction $^{18}$F(d,$α$ $^{15}$O)n at the low energies relevant for astrophysics. The abundance of $^{18}$F in Nova explosions is an important issue for the understanding of this astrophysical phenomenon. For this reason it is necessary to study the nuclear reactions that produce or destroy $^{18}$F in Novae. $^{18}$F(p,$α$)$^{15}$O is one of the main $^{18}$F destruction channels. Preliminary results are presented in this paper.

nucl-ex↗

arXiv2011

Molecular Structures in T=1 states of 10B

Multi-center (molecular) structures can play an important role in light nuclei. The highly deformed rotational band in 10Be with band head at 6.179 MeV has been observed recently and suggested to have an exotic alpha:2n:alpha configuration. A search for states with alpha:pn:alpha two-center molecular configurations in 10B that are analogous to the states with alpha:2n:alpha structure in 10Be has been performed. The T=1 isobaric analog states in 10B were studied in the excitation energy range of E=8.7-12.1 MeV using the reaction 1H(9Be,alpha)6Li*(T=1, 0+, 3.56 MeV). An R-matrix analysis was used to extract parameters for the states observed in the (p,alpha) excitation function. Five T=1 states in 10B have been identified. The known 2+ and 3- states at 8.9 MeV have been observed and their partial widths have been measured. The spin-parities and partial widths for three higher lying states were determined. Our data support theoretical predictions that the 2+ state at 8.9 MeV (isobaric analog of the 7.54 MeV state in 10Be) is a highly clustered state and can be identified as a member of the alpha:np:alpha rotational band. The next member of this band, the 4+ state, has not been found. A very broad 0+ state at 11 MeV that corresponds to pure alpha+6Li(0+,T=1) configuration is suggested and it might be related to similar structures found in 12C, 18O and 20Ne.

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arXiv2010

Measurements of nuclear $γ$-ray line emission in interactions of protons and $α$ particles with N, O, Ne and Si

$γ$-ray production cross sections have been measured in proton irradiations of N, Ne and Si and $α$-particle irradiations of N and Ne. In the same experiment we extracted also line shapes for strong $γ$-ray lines of $^{16}$O produced in proton and $α$-particle irradiations of O. For the measurements gas targets were used for N, O and Ne and a thick foil was used for Si. All targets were of natural isotopic composition. Beams in the energy range up to 26 MeV for protons and 39 MeV for $α$-particles have been delivered by the IPN-Orsay tandem accelerator. The $γ$ rays have been detected with four HP-Ge detectors in the angular range 30$^{\circ}$ to 135$^{\circ}$. We extracted 36 cross section excitation functions for proton reactions and 14 for $α$-particle reactions. For the majority of the excitation functions no other data exist to our knowledge. Where comparison with existing data was possible usually a very good agreement was found. It is shown that these data are very interesting for constraining nuclear reaction models. In particular the agreement of cross section calculations in the nuclear reaction code TALYS with the measured data could be improved by adjusting the coupling schemes of collective levels in the target nuclei $^{14}$N, $^{20,22}$Ne and $^{28}$Si. The importance of these results for the modeling of nuclear $γ$-ray line emission in astrophysical sites is discussed.

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arXiv2009

New High-Precision Measurement of the Reaction Rate of the 18O(p,alpha)15N Reaction via THM

The 18O(p,alpha)15N reaction rate has been extracted by means of the Trojan-Horse method. For the first time the contribution of the 20-keV peak has been directly evaluated, giving a value about 35% larger than previously estimated. The present approach has allowed to improve the accuracy of a factor 8.5, as it is based on the measured strength instead of educated guesses or spectroscopic measurements. The contribution of the 90-keV resonance has been determined as well, which turned out to be of negligible importance to astrophysics.

astro-ph.SR↗

arXiv2008

Measurement of the 20 and 90 keV resonances in the ${}^{18}{\rm O}(p,α){}^{15}$N reaction via THM

The $^{18}{\rm O}(p,α)^{15}{\rm N}$ reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside AGB stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the $^{18}{\rm O}(p,α)^{15}{\rm N}$ reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances have been deduced and the change in the reaction rate evaluated.

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