Proton capture to excited states of /sup 16/O; Ml, El and Gamow-Teller transitions and shell-model calculations

Technical Report · Fri Jan 01 04:00:00 EST 1982

OSTI ID:6235904

Snover, K A; Adelberger, E G; Ikossi, P G; Brown, B A

We have measured excitation functions of the ..gamma..-rays resulting from the bombardment of /sup 15/N by polarized and unpolarized protons in the energy range E/sub p/ = 2.5 to 9.5 MeV with emphasis on identifying dipole decays to the first (0/sup +/) and second (3/sup -/) excited states in /sup 16/O. Resonances in ..gamma../sub 12/ are observed at E/sub x/ = 16.21, 16.45, 16.82, 17.12, 18.03, 18.98, 19.90 and 20.41 MeV. The 16.21 and 17.12 MeV resonances in ..gamma../sub 12/ are identified as M1-decays of the 1/sup +/ T = 1 states to the 6.05 MeV 0/sup +/ state in /sup 16/O. The measured ratio of reduced strengths B(m1,..gamma../sub 1/)/(B(M1,..gamma../sub 0/) is 0.48 +- 0.03 for decays from the 16.21 MeV state and 0.55 +- 0.04 for decays from the 17.12 MeV state. The 18.03 MeV resonance is due to a 3/sup -/ T = 1 state in /sup 16/O with a strength Gamma/sup p/Gamma/sub gamma 2//Gamma = (1.96 +- 0.27) eV and the 18.98 MeV resonance is due to the 4/sup -/ T = 1 stretched particle-hole state with a strength of (0.85 +- 0.10) eV. We determine absolute particle and ..gamma.. widths for these states. The M1 ..gamma../sub 2/-width of the 18.98 MeV state, (7.1 +- 3.1) eV, is in agreement with a shell-model calculation. Resonances in ..gamma../sub 3/ are observed at 16.82 and 17.27 MeV and in ..gamma../sub 4/ at 17.88 MeV. The excitation energies and widths of these levels as well as the strengths of the ..gamma.. transitions suggest T = 1 character for all of the resonances for which capture ..gamma..-rays are observed. Correspondences of our resonances to levels in /sup 16/N are given. We compare ..gamma.. widths, including ground-state M1 decays, and allowed ..beta.. transition rate in A = 16 nuclei with shell model calculations and obtain rough agreement. Additional shell model calculations for M1 and GT (Gamow-Teller) decays in the A-14, 15, 17 and 18 nuclei are presented, which indicate that GT matrix elements are quenched by approx. 20% relative to shell model predictions and also relative to the spin part of the M1 matrix elements.

• Research Organization: Washington Univ., Seattle (USA). Nuclear Physics Lab.; Oxford Univ. (UK). Nuclear Physics Lab.; Michigan State Univ., East Lansing (USA). Cyclotron Lab.
• DOE Contract Number: AC06-81ER40048
• OSTI ID: 6235904
• Report Number(s): DOE/ER/40048-32-L2; ON: DE83011480
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARYON REACTIONS
BEAMS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CAPTURE
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DATA
E1-TRANSITIONS
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
EXCITATION FUNCTIONS
EXPERIMENTAL DATA
FUNCTIONS
GAMMA RADIATION
GAMMA SPECTRA
GAMOW-TELLER RULES
HADRON REACTIONS
INFORMATION
IONIZING RADIATIONS
ISOTOPES
LIGHT NUCLEI
M1-TRANSITIONS
MATHEMATICAL MODELS
MEV RANGE
MEV RANGE 01-10
MULTIPOLE TRANSITIONS
NITROGEN 15 TARGET
NITROGEN 16
NITROGEN ISOTOPES
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
NUMERICAL DATA
ODD-ODD NUCLEI
OXYGEN 16
OXYGEN ISOTOPES
POLARIZED BEAMS
PROTON REACTIONS
RADIATIONS
RADIOISOTOPES
RESONANCE
SECONDS LIVING RADIOISOTOPES
SHELL MODELS
SPECTRA
STABLE ISOTOPES
STRENGTH FUNCTIONS
TARGETS
THEORETICAL DATA