Electromagnetic M1 Transition Strengths from Inelastic Proton Scattering: The Cases of 48 Ca and 208 Pb

Summary.{A new method for the extraction of spin-ipM1 strength from inelastic proton scattering at forwardangles has been presented relating it to the GT strengthstudied with the analog (p;n) reaction. The underlyingapproximations were shown to be well justi ed for thecase of the prominent transition in 48 Ca. The extractedB(M1) strength in 48 Ca agrees with the (e;e 0 ) result [20].The much larger value from a recent (;n) experiment[22] is clearly in conict with the precise (e;e 0 ) and (p;p 0 )results derived by completely independent methods. Ap-plication to 208 Pb shows again good agreement with elec-tromagnetic probes and also highlights the sensitivity ofthe new method above the neutron threshold, where sig-ni cant additional strength is found not accessible in theprevious work. This nding has important consequencesfor an understanding of the quenching of the spin-isospinresponse, which will be discussed in a forthcoming pa-per. Systematic studies with this new experimental toolare under way (including a detailed comparison with re-sults from electromagnetic probes for