Experimental constraints on size and phase of proton and neutron contributions to the isoscalar 1+ state in208Pb

The 1⁺ state at 5.846 MeV in²⁰⁸Pb was observed in a high-resolution²⁰⁹Bi(d³He)²⁰⁸Pb experiment with a spectroscopic factor of C²S=0.17. From this, together with the transition probability BM1↑=1.6μ _N ² from a ( ((vec gamma ,gamma ')) ) experiment and the normalization condition we derive size and relative phase of proton and neutron spinflip amplitudes of the 1⁺ state wave function; these are in good agreement with predictions of TDA and RPA calculations. Presumably only few nuclear states have ever been subject to so much interest from both theoretical and experimental sides as the lowest 1⁺ state in²⁰⁸Pb [1]. The reasons are the expected simplicity of its configuration and that its energy and particle-hole structure allow one to expect information on the spin-dependent parts of the residual interaction. It is the aim of the present work to determine the leading terms of the wave function of the 1 state directly from experimental results without making essential assumptions, in contrast to previous analyses.