The 5/2⁻ Resonance at 850 keV in ¹⁵N(α,γ)¹⁹F

Abstract

A weak resonance at 850 keV in 15N(a,y)19F corresponding to a level at 4681 f 1 keV in I9F has been found. Angular distributions and Doppler shifts have been measured for the primary decays to the 512-level at 1.35 MeV (63%), 312-level at 1.46 MeV (31%). and the 5/2+ level at 197 keV (6%). A spin of 512 has been assigned to the resonance level and negative parity is shown to be very likely. The lifetime of the resonance was measured by the Doppler shift attenuation method to be T = (15.4 f 3.0) x 10-l5 s or r = 42.8 + 8.5 meV. The measured value of my was 6.0 + 1.0 meV. These measurements together with previous -information on r , / r imply the observed MI transition strengths are a factor of 20 weaker than predicted for the 512 member of the K = 312-band in I9F which has previously been associated with this level. Une faible resonance a 850 keV dans 15N(a,y)LgF correspondant a un niveau a 4681 + I keV dans le IyF a ete trouvee. Les distributions angulaires et les effets Doppler ont Cte mesures pour les desintegrations primaires vers le niveau 512-a 1.35 MeV (63%), le niveau 312-a 1.46 MeV (31 %) et le niveau 5/2+ a 197 keV (6%).Un spin 512 a it6 attribuC au niveau de resonance et on montre qu'une parite negative est tris probable. La vie rnoyenne de la resonance a ete evaluk par la methode de I'atttnuation de I'effet Doppler a r = (15.4 f 3.0) x 10-l5 sou r = 42.8 + 8.5 MeV. La valeur rnesuree de wy est 6.0 + 1.0 meV. Ces mesures ainsi que I'inforrnation anterieurs sur T,/T irnpliquent que les forces de transition M1 observees sont plus faibles par un facteur 20 que celles predites pour le rnernbre 512 de la bande K = 312-dans le "F qui a ete anterieurement associe a ce niveau.

Charged-particle thermonuclear reaction rates: II. Tables and graphs of reaction rates and probability density functions

“…1). Total widths are deduced from the averaged DSAM lifetime measured values [196,225,140,179], except for the first two resonances at 505 and 849 keV, for which the results of Davids et al [57] are used. Alpha-particle partial widths are calculated using the α-particle branching ratios adopted by Ref.…”

Energy levels of light nuclei A = 18–20

“…The yield of 18 F [reaction (b)] has been determined for E( 7 Li) = 2.5 to 3.5 MeV (1961NO05). The yields of α-particles have been measured by (1962HO06; 1.35 1972RO01) 0.197…”

Study of 19F by -15N plus t-16O Coupled Channel Orthogonality Condition Model. II: Electromagnetic Transitions and Spectroscopic Factors

“…The present model space is spanned by the wave functions: (8) where hi < 112 LlJ is a channel wave function and RNi (ri) is the h.o. wave function used as a basis function for the relative motion.…”