  Fluorine is a key element for nucleosynthetic studies since it is extremely
sensitive to the physical conditions within stars. The astrophysical site to
produce fluorine is suggested to be asymptotic giant branch (AGB) stars. In
these stars the 15N(n, g)16N reaction could affect the abundance of fluorine by
competing with 15N(a, g)19F. The 15N(n, g)16N reaction rate depends directly on
the neutron spectroscopic factors of the low-lying states in 16N. The angular
distributions of the 15N(7Li, 6Li)16N reaction populating the ground state and
the first three excited states in 16N are measured using a Q3D magnetic
spectrograph and are used to derive the spectroscopic factors of these states
based on distorted wave Born approximation (DWBA) analysis. The spectroscopic
factors of these four states are extracted to be 0.96+-0.09, 0.69+-0.09,
0.84+-0.08 and 0.65+-0.08, respectively. Based on the new spectroscopic factors
we derive the 15N(n,g)16N reaction rate. The accuracy and precision of the
spectroscopic factors are enhanced due to the first application of
high-precision magnetic spectrograph for resolving the closely-spaced 16N
levels which can not be achieved in most recent measurement. The present result
demonstrates that two levels corresponding to neutron transfers to the 2s1/2
orbit in 16N are not so good single-particle levels although 15N is a closed
neutron-shell nucleus. This finding is contrary to the shell model expectation.
The present work also provides an independent examination to shed some light on
the existing discrepancies in the spectroscopic factors and the 15N(n, g)16N
rate.
