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 ≤ 511 keV gamma-ray emission depends critically on the 18 F(p,α) 15 O reaction rate which, despite many experimental and theoretical efforts, still remains uncertain.Purpose: One of the main uncertainties in the 18 F(p,α) 15 O reaction rate is the contribution in the Gamow window of interference between sub-threshold 19 Ne states and known broad states at higher energies. Therefore the goal of this work is to clarify the existence and the nature of these sub-threshold states.Method: States in the 19 Ne compound nucleus were studied at the Tandem-ALTO facility using the 19 F( 3 He,t) 19 Ne charge exchange reaction. Tritons were detected with an Enge Split-pole spectrometer while decaying protons or α-particles from unbound 19 Ne states were collected, in coincidence, with a double-sided silicon strip detector array. Angular correlations were extracted and constraints on the spin and parity of decaying states established. Results:The coincidence yield at Ex = 6.29 MeV was observed to be high spin, supporting the conclusion that it is indeed a doublet consisting of high spin and low spin components. Evidence for a broad, low spin state was observed around 6 MeV. Branching ratios were extracted for several states above the proton threshold and were found to be consistent with the literature. R-matrix calculations show the relative contribution of sub-threshold states to the astrophysically important energy region above the proton threshold. Conclusions:The levels schemes of 19 Ne and 19 F are still not sufficiently well known and further studies of the analogue assignments are needed. The tentative broad state at 6 MeV may only play a role if the reduced proton width is large.

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