The linearly polarized γ-ray beam produced by the $\mathrm{HI}\gamma \mathrm{S}$ facility has been used to determine the parity of two previously known dipole excitations in ${}^{88}\mathrm{Sr}.$ The azimuthal asymmetry of γ rays produced in the process of nuclear resonance fluorescence indicated that the dipole state at 4.742 MeV, recently discussed as a new form of $M1\mathrm{}$ excitation, is in fact a $1^{-}$ $\mathrm{}\left(E1\mathrm{}\right)\mathrm{}$ state. The $1^{-}$ state at 4.742 MeV must, therefore, be reconsidered as the $J^{\pi }{=1\mathrm{}}^{-}$ member of the quadrupole-octupole coupled two-phonon multiplet. A second state at 7.535 MeV was also assigned $J^{\pi }{=1\mathrm{}}^{-}.$

• Received 18 January 2002

DOI:https://doi.org/10.1103/PhysRevC.65.047305