Evidence is presented for five closely spaced states in ${}_{}{}^{118}{}_{}{}^{}\mathrm{Cd}$ near $E_{\mathrm{ex}\mathrm{\simeq }2}$ MeV, which are interpreted as a near-harmonic three-phonon quintuplet. Candidates for even higher-lying multiphonon states are also found. The experimental spectrum is compared with an anharmonic vibrator [or U(5) spectrum] and an interacting-boson-approximation calculation incorporating a two-particle, four-hole intruder configuration.

• Received 4 May 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.535