Lifetime measurement of the 6792 keV state in 15O, important for the astrophysical S factor extrapolation in 14N(p, γ)15O

We report on a new lifetime measurement of the E-x = 6792 keV state in O-15 via the Doppler-shift attenuation method at the E = 259 keV resonance in the reaction N-14(p, gamma)O-15. This subthreshold state is of particular importance for the determination of the ground state astrophysical S factor of N-14(p, gamma)O-15 at stellar energies. The measurement technique has been significantly improved over that used in previous work. The conclusion of a finite lifetime drawn there cannot be confirmed with the present data. In addition, the lifetimes of the two states at E-x = 5181 and 6172 keV have been measured with the same technique in order to verify the experimental method. We observe an attenuation factor F(tau) > 0.98 for the E-x = 6172 and 6792 keV states, respectively, corresponding tau < 0.77 fs. The attenuation factor for the E-x = 5181 keV state results in F(tau) = 0.78 +/- 0.02 corresponding to tau = 8.4 +/- 1.0 fs, which is in excellent agreement with literature.