Mesure dans le $^{19}$Ne des résonances d’intérêt pour l’´étude des novæ par une nouvelle méthode de diffusion inélastique

Abstract : A nova is a thermonuclear runaway occurring in binary system of stars. The observation of the gamma rays emitted after a nova is a way to better understand this phenomenon. According to the models, the line at 511 keV, produced in the annihilation between positrons and electrons, would be the most intense line several hours after the explosion. One of the main positron emitters would be the $^{18}$F radioactive isotope. In order to improve the predictive power of the models, it is crucial to better determine the amount of $^{18}$F produced in the nova. Yet, the $^{18}$F destruction rate $^{18}$F(p,$\alpha$)$^{15}$O is given with large uncertainties. Measuring the spectroscopic properties (energy, width, spin) of states in the compound nucleus 19Ne should allow us to constrain the reaction rate. In this context, an experiment based on a new inelastic scattering method ($^{19}$Ne(p,p’)$^{19}$Ne∗) was performed at GANIL with the VAMOS spectrometer. The detection system has been adapted to detect for the first time high energy protons (p’). A good energy resolution in inverse kinematic has been reached ($\sigma$=33 keV). The angular distribution measurement of decaying particles should provide the spin assignment of the states in a model independent way. Unfortunately, an unforeseen contamination has prevented us to complete this measurement. New spectroscopic information have been extracted and contributed to reduce the uncertainty of the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate in a significant way. The data are compatible with a new broad state below the proton threshold (6.41 MeV). This state seems to be sufficiently broad to contribute to the destruction reaction rate of $^{18}$F and reduces the chances for satellite detection.
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Submitted on : Friday, January 8, 2016 - 2:59:09 PM
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F. Boulay. Mesure dans le $^{19}$Ne des résonances d’intérêt pour l’´étude des novæ par une nouvelle méthode de diffusion inélastique. Physique Nucléaire Expérimentale [nucl-ex]. Université de Caen Normandie, 2015. Français. ⟨tel-01252983⟩

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