Comprehensive studies of low-spin collective excitations in ⁹⁴Mo

Excited low-spin states in ⁹⁴Mo have been studied extensively with a combination of γ-ray spectroscopic techniques. We have performed photon scattering experiments, γγ coincidence measurements following the β⁺ decay of ⁹⁴Tc^m, in-beam γγ coincidence studies with the reaction ⁹¹Zr(α,n)⁹⁴Mo, and ⁹⁴Mo(n,n′ γ) measurements. These experiments yielded detailed information about the low-spin level scheme of ⁹⁴Mo. From measured lifetimes, branching ratios, and multipole mixing ratios, many absolute transition strengths were determined. These data permitted the interpretation of several low-spin states in terms of collective excitations, that are not fully symmetric with respect to the proton-neutron degree of freedom, the so-called mixed-symmetry (MS) states: The one-phonon 2⁺ MS state and three members of an expected multiplet of two-phonon MS states were identified from absolute M l and E2 transition strengths. The data also enable us to identify several proton-neutron-symmetric multiphonon states.