Resonant two proton decay from 14 O using a radioactive beam
Date
1995Author
Bain, Carlos
Metadata
Abstract
Two experiments were carried out to search for and identify the mechanism for
two proton emission from the 7.77 MeV excited state
in 14 O. The experiments were performed at the Radioactive Ion Beams Facility at
LouvainlaNeuve, in Belgium, using a 45 MeV beam of radioactive 13 N 3+ ions on a
[CH 2 ] n target to populate the state. The protons and other particles were detected
using the LouvainEdinburgh Detector Array, LEDA, a large area annular silicon
strip detector. Control experiments with a 12 C target and with a degraded beam
energy were also made.
Protonproton coincidence measurements made in the commissioning run iden
tified a two proton decay component. However, the large background (~90%)
caused by evaporation protons from the fusion of 13 N with 12 C prevented an analysis of the decay mechanism.
The follow up experiment utilised two LEDA detectors whereby the protons of
interest would be stopped in the front detector with the back detector acting
as a veto for high energy protons. Comparison of data with simulations for the
decay mechanisms revealed the decay to be dominantly a sequential emission of
two protons via the 2.37 MeV state in 13 N to the ground state in 12 C. This decay mode has a measured partial width of
125\Sigma20 eV which represents a 0.16% branching ratio. Theoretical predictions
for this value give a width of 3 \Sigma 1 keV which gives a spectroscopic factor of
` 2 = 0:04. Simulations using a model for 2 He or diproton emission have resulted
in an upper limit of 5% being set which corresponds to ~6 eV (95% confidence
limit). Calculation for this width with a spectroscopic factor of unity give a value
of 15\Sigma5 eV. Hence an upper limit for the spectroscopic factor of theta2 = 0:4 can be
set which is above the value of 0.22 predicted by B.A. Brown.