Sub-threshold states in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ne</mml:mi><mml:mprescripts /><mml:none /><mml:mn>19</mml:mn></mml:mmultiscripts></mml:math> relevant to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">F</mml:mi><mml:mprescripts /><mml:none /><mml:mn>18</mml:mn></mml:mmultiscripts><mml:mo>(</mml:mo><mml:mi>p</mml:mi><mml:mo>,</mml:mo><mml:mi>α</mml:mi><mml:mo>)</mml:mo><…

Background: Classical novae result from thermonuclear explosions producing several γ-ray emitters which are prime targets for satellites observing in the MeV range. The early ≤511keV emission depends critically on F18(p,α)O15 reaction rate which, despite many experimental and theoretical efforts, still remains uncertain. Purpose: One of main uncertainties is contribution Gamow window interference between sub-threshold Ne19 states known broad at higher energies. Therefore goal this work to clarify existence nature these states. Methods: States compound nucleus were studied Tandem-ALTO facility using F19(He3,t)Ne19 charge-exchange reaction. Tritons detected with an Enge Split-pole spectrometer while decaying protons or α particles unbound collected, coincidence, a double-sided silicon strip detector array. Angular correlations extracted constraints spin parity established. Results: coincidence yield Ex=6.29MeV was observed be high spin, supporting conclusion that it indeed doublet consisting high-spin low-spin components. Evidence broad, state around 6 MeV. Branching ratios above proton threshold found consistent literature. R-matrix calculations show relative astrophysically important energy region threshold. Conclusions: levels schemes F19 not sufficiently well further studies analog assignments needed. tentative may only play role if reduced width large.2 MoreReceived 28 July 2020Accepted 27 October 2020DOI:https://doi.org/10.1103/PhysRevC.103.015807©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCharge-exchange reactionsNuclear astrophysicsNuclear physics explosive environmentsNuclear structure & decaysProperties6 ≤ A 19TechniquesSpectrometers spectroscopic techniquesNuclear Physics