Lifetime measurement of the 6792 keV state inO15, important for the astrophysicalSfactor extrapolation inN14(p,γ)O15

Abstract

We report on a new lifetime measurement of the ${E}_{x}=6792$ keV state in $^{15}\mathrm{O}$ via the Doppler-shift attenuation method at the $E=259$ keV resonance in the reaction $^{14}\mathrm{N}$($p,\ensuremath{\gamma}$)$^{15}\mathrm{O}$. This subthreshold state is of particular importance for the determination of the ground state astrophysical $S$ factor of $^{14}\mathrm{N}$($p,\ensuremath{\gamma}$)$^{15}\mathrm{O}$ 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 $F(\ensuremath{\tau})>0.98$ for the ${E}_{x}=6172$ and 6792 keV states, respectively, corresponding to $\ensuremath{\tau}<0.77$ fs. The attenuation factor for the ${E}_{x}=5181$ keV state results in $F(\ensuremath{\tau})=0.78\ifmmode\pm\else\textpm\fi{}0.02$ corresponding to $\ensuremath{\tau}=8.4\ifmmode\pm\else\textpm\fi{}1.0$ fs, which is in excellent agreement with literature.