Parity assignments inYb172,174using polarized photons and theKquantum number in rare earth nuclei

The 100% polarized photon beam at the high intensity {gamma} ray source (HI{gamma}S) at Duke University has been used to determine the parity of six dipole excitations between 2.9 and 3.6 MeV in the deformed nuclei {sup 172,174}Yb in photon scattering ({gamma}{sup {yields}},{gamma}{sup '}) experiments. The measured parities are compared with previous assignments based on the K quantum number that had been assigned in nuclear resonance fluorescence (NRF) experiments by using the Alaga rules. A systematic survey of the relation between {gamma}-decay branching ratios and parity quantum numbers is given for the rare earth nuclei.