Alpha-particle decay branching ratio measurements for excited states of [sup 15]N

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7005651

Liendo, J A

The reactions, [sup 12]C([sup 7]Li,[alpha])[sup 15]N and [sup 7]Li([sup 12]C,[sup 15]N [yields] [alpha] + [sup 11]B)[alpha] at E[sub cm] = 33.2 MeV, are used to measure the alpha-particle decay branching ratio, [Gamma][sub [alpha]]/[Gamma], of states in [sup 15]N produced at several excitation energies, E[sub x]([sup 15]N). Resonant Particle Decay Spectroscopy is applied to the sequential reaction to identify [sup 15]N states and construct their alpha-particle angular correlations from the kinematic reconstruction of the relative kinetic energy of the [sup 15]N break-up products ([alpha] and [sup 11]B) detected in coincidence by use of two position sensitive detectors. It is shown that the symmetry observed in these correlations implies azimuthal isotropy, so that integration can be accomplished to yield [Gamma][sub [alpha]]/[Gamma] in conjunction with the measured [sup 15]N production cross sections. For excited states at E[sub x]([sup 15]N) = 11.44, 12.56, 13.01, 13.18, 13.83 and 14.11 MeV, the measured values of [Gamma][sub [alpha]]/[Gamma] are 0.07 [+-] 0.01, 0.60 [+-] 0.04, 0.84 [+-] 0.09, 0.34 [+-] 0.04, 0.37 [+-] 0.09 and 0.31 [+-] 0.06 respectively (absolute uncertainty is [approximately]15%). Reduced widths of some of these states are calculated under limiting approximations. Spectral analysis also yields: (a) New excited states at E[sub x]([sup 15]N) = 12.67, 12.83, 15.15 and 22.58 (MeV), (b) confirmation of previously unknown alpha-particle decays for 17 excited states and (d) correction of previously reported energy widths for states at E[sub x]([sup 15]N) = 16.20, 16.46, 17.12, and 20.955 MeV. Probable spin-parity values are proposed for several [sup 15]N states based on a DWBA analysis carried out for the angular distributions of the [sup 12]C([sup 7]Li, [alpha])[sup 15]N reaction and the best theoretical descriptions of the alpha-particle angular correlations of the sequential reaction.

• Research Organization: Florida State Univ., Tallahassee, FL (United States)
• OSTI ID: 7005651
• Country of Publication: United States
• Language: English

Related Subjects

663210* -- Ground-State Radioactivity-- (1992-)
663520 -- Nuclear Mass Ranges-- A=6-19-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA DECAY
BRANCHING RATIO
CARBON 12 REACTIONS
CHARGED-PARTICLE REACTIONS
DECAY
ENERGY LEVELS
ENERGY RANGE
EXCITED STATES
HEAVY ION REACTIONS
ISOTOPES
LIGHT NUCLEI
LITHIUM 7 REACTIONS
MEV RANGE
MEV RANGE 10-100
NITROGEN 15
NITROGEN ISOTOPES
NUCLEAR DECAY
NUCLEAR REACTIONS
NUCLEI
ODD-EVEN NUCLEI
STABLE ISOTOPES