A study of Gamow-teller strength using the 208Pb(p,n) and 181Ta(p,n) reactions at intermediate energy, Ep=122 MeV

The Gamow-Teller strength was measured in ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions at an incident proton energy of 122 MeV. The experiment was performed using the beam-swinger facility at the National Accelerator Centre, Faure, South Africa. The time-of-flight(TOF) technique was employed with a flight-path of 100 m. Detectors comprised three stacks of four rectangular bars of NE 102A plastic scintillators. The outgoing neutrons were observed at laboratory angles, ΘLab = 0°, 2°, 4° and 10° . A multipole decomposition analysis of spectra associated with ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions was performed using the results of distorted-wave impulse approximation (DWIA) calculations. The spectra associated with the two reactions were decomposed into L=0,1 and 2 transfer components. The major contribution to the spectra were found to be L=O, with a very small 1=2 multipole transfer contribution. The spectra were modelled with a combination of symmetrical Gaussians and a polynomial background. The GT strength was extracted by normalizing the cross section of the GT states to the cross section of the isobaric analogue state. The ΣB(GT) strength associated with the ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions was found by summing the individual GT strength in the 0 - 23 MeV and 0 - 20 MeV excitation regions respectively. The ΣB(GT) strength associated with the ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions were found to be less than the values predicted by the 3(N - Z) sum rule, being 81 ± 10% and 78 ± 3% of the sum rule strength respectively.

Grantor dc:publisher.institution

Department of Physics

Year dc:date.issued

1997

Author dc:creator

• Tshivhase, Victor Makondelele

Advisor dc:contributor.advisor

• Aschman, David G

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/17971

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/17971