Neutron decay from the giant resonance via the {sup 10}B(e,e{sup '}n) reaction
- Department of Physics, Yamagata University, Kojirakawa, Yamagata 990-8560 (Japan)
The cross sections and angular correlations for neutron decay into various states in the residual nucleus following the {sup 10}B(e,e{sup '}n) reaction have been measured over the excitation energy range of 18-33 MeV at an effective momentum transfer of 0.56 fm{sup -1}. In the giant resonance, neutron emission leads to the population of two higher excited states in addition to the ground-state transition: 6.97 MeV 7/2{sup -}(n{sub 5}) and 11.70 MeV 7/2{sup -}+12.06 MeV 3/2{sup -}(n{sub 6,7}). This is the first observation of the neutron population of these states. The angular correlations for n{sub 0} show a strong forward-backward asymmetry, which suggests interference from a transition with the opposite parity to E1. The angular correlations for n{sub 5} and n{sub 6,7} have a peak shift of about 50 deg. at lower excitation energy and recover above about 24 and 25 MeV for n{sub 5} and n{sub 6,7}, respectively. Their patterns are considerably different from that for n{sub 0}. The angular correlations for each transition were fitted with a Legendre polynomial. The longitudinal-transverse interference coefficient C{sub 2}/A{sub 0} is negligible for all populations. For n{sub 0} decay, all Legendre coefficients b{sub i} are positive, but b{sub 2} and b{sub 3} for the n{sub 5} and n{sub 6,7} decays are negative at lower excitation energy, and the latter causes a shift of the forward peak. The negative values may come from the signs of the phase differences of cos{delta}{sub 21} and cos{delta}{sub 20}. The {sup 10}B(e,e{sup '}n) cross section measured up to E{sub x}{approx}32 MeV agrees well with that of {sup 10}B({gamma},n), except for a peak at 23 MeV of the giant resonance. In comparison with shell-model calculations, the partial cross section for n{sub 0} is sizable up to higher excitation energy, and predicted large partial cross sections populating the 6.97 MeV 7/2{sup -} and 11.70 MeV 7/2{sup -}+12.06 MeV 3/2{sup -} states in the giant resonance were not observed.
- OSTI ID:
- 21296600
- Journal Information:
- Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 6 Vol. 80; ISSN 0556-2813; ISSN PRVCAN
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANGULAR CORRELATION
ASYMMETRY
BORON 10 TARGET
COMPARATIVE EVALUATIONS
CROSS SECTIONS
DECAY
EXCITATION
EXCITED STATES
GIANT RESONANCE
GROUND STATES
INTERFERENCE
LEGENDRE POLYNOMIALS
MEV RANGE 10-100
MOMENTUM TRANSFER
NEUTRON EMISSION
NEUTRONS
PARITY
SHELL MODELS