Phys. Rev. C 63, 014603 (2000) [9 pages]Observation of the spin isovector monopole resonance using the Pb(p⃗,n⃗)Bi reaction at 795 MeVReceived 9 June 2000; published 18 December 2000 We examine a broad resonance in the 0° 208Pb(p,n)208Bi and 90Zr(p,n)90Nb cross section spectra obtained at 795 MeV incident energy that appears at 32 MeV excitation energy in 208Bi and 90Nb. Earlier data taken at 200 MeV incident energy using the same reactions show no evidence for this resonance. We present theoretical results indicating that the spin isovector monopole predicted at this excitation energy is barely excited at 200 MeV while it is strongly excited at the higher energy. To further investigate this structure we have measured the first complete set of polarization-transfer observables for natPb at 0° using the (p⃗,n⃗) reaction at 795 MeV. The data show this resonance is predominantly a spin flip ΔS=1 excitation giving strong supporting evidence for assigning this resonance as the spin isovector monopole. © 2000 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevC.63.014603
DOI:
10.1103/PhysRevC.63.014603
PACS:
24.30.Cz, 25.40.Kv, 27.60.+j, 27.80.+w
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