J. S. Forster

Mass excess and low-lying level structure of

The mass excess of /sup 14/B has been measured to be 23.657 plus or minus 0.030 MeV using the reaction /sup 14/C(/sup 7/Li,)/sup 14/B at E(/sup 7/Li) - 52 MeV ; this shows that /sup 14/B is bound by nearly 1 MeV against neutron emission. Five excited states were also observed at 0.74 plus or minus 0.04, 1.38 plus or minus 0.03, 1.82 plus or minus O.06, 2.08 plus or minus .05, and 2.97 plus or minus 0.04 MeV. The low-lying level structure of /sup 14/B wa s found to be similar to the known negative-parity spectrum of /sup 12/B. (auth)

sup 14

The 15 O(α, γ) 19 Ne reaction plays a role in the ignition of type I x-ray bursts on accreting neutron stars. The lifetimes of states in 19 Ne above the 15 O+α threshold of 3.53 MeV are important inputs to calculations of the astrophysical reaction rate. These levels in 19 Ne were populated in the 3 He( 20 Ne , α) 19 Ne reaction at a 20 Ne beam energy of 34 MeV. The lifetimes of six states above the threshold were measured with the Doppler-shift attenuation method. The present measurements agree with previous determinations of the lifetimes of these states and in some cases are considerably more precise.