High-energy-resolution inelastic electron scattering (at the S-DALINAC) and proton scattering (at iThemba LABS) experiments permit a thorough test of the nature of proposed one-and two-phonon symmetric and mixed-symmetric 2 states of the nucleus 94 Mo. The combined analysis reveals the onephonon content of the mixed-symmetry state and its isovector character suggested by microscopic nuclear model calculations. The purity of two-phonon 2 states is extracted. DOI: 10.1103/PhysRevLett.99.092503 PACS numbers: 21.10.Re, 25.30.Dh, 25.40.Ep, 27.60.+j Collective valence-shell excitations are a generic feature of strongly-coupled mesoscopic quantum systems. A prime example of a two-component system is the atomic nucleus formed by protons and neutrons. The microscopic structure of collective nuclear excitations with respect to their proton-neutron content is a central issue of nuclear structure physics with general implications for the physics of composite strongly-coupled quantum systems. Low-energy nuclear valence-shell excitations usually possess the lowest possible isospin quantum number T < jN ÿ Zj=2. Nevertheless, the symmetry character of their proton-neutron coupling can vary. This fact is evident in the framework Recently, one-and two-phonon MSSs were investigated in vibrational nuclei with proton and neutron numbers near closed shells, e.g., in the nuclide 94 Mo [5]. Comprehensive spectroscopic information on low-spin states has been achieved up to an excitation energy of about 4 MeV It is the purpose of this Letter to report a combined study of electron and proton scattering differential cross sections for J 2 one-and two-phonon FSSs and MSSs in 94 Mo. The selectivity of both reactions to one-phonon components in the excited state wave functions allows to extract for the first time the small one-phonon contributions to the two-phonon candidates. The proton-neutron symmetry character can be derived since electron scattering couples to the proton distributions, while proton scattering is dominated by the isoscalar central part of the effective proton-nucleus interaction. We thereby introduce a new approach establishing a multiphonon character of nuclear MSSs based on scattering data complementary to -ray spectroscopy. The (e; e 0 ) experiments were carried out at the highenergy-resolution magnetic spectromete
