ENDOR and relaxations in systems with I=S=1/2:169Tm2+and171Yb3+in CaF2

Abstract

It is shown that equal intensities of the two ENDOR transitions for 169Tm2+ and 171Yb3+ in CaF2 indicate that the relaxation rates Tx-1( mod 1/2,-1/2( to or from mod -1/2,-1/2)) and Tx'-1( mod 1/2, 1/2( to or from mod -1/2,-1/2)) are approximately equal. The relative simplicity of the wavefunctions for the 4f13 configuration in a cubic crystal field, and of the Hamiltonian for the orbit-lattice interaction, enables one to make an explicit calculation of the various relaxation rates in terms of the orbit lattice parameters V( Gamma i,l). Matrix elements of the hyperfine interaction between ground and excited states of the J=7/2 manifold are found to be important in leading to calculated values for Tx-1 which are comparable to those for Tx'-1. Similar magnitudes for Tx-1 and Tx'-1 are shown to be expected for systems with large components of unquenched orbital angular momentum, in contrast to systems with little orbital angular momentum where Tx'-1 approximately=0.