Electron nuclear double resonance of the divalent europium ion

Abstract

The electron nuclear double resonance spectrum of both isotopes 151 Eu and 163 Eu has been measured in a single crystal of calcium fluoride containing about 0.01 % Eu 2+ . As the lines were narrow ( ~ 10kc/s) the hyperfine structure parameter and the nuclear g-value were measured to high precision giving the following values: A 151 = -102.9069±0.0013 Mc/s, A 153 = -45.6730±0.0025 Mc/s B 151 = -0.7855±0.0052 Mc/s, B 153 = -2.0294 ±0.0068 Mc/s, gI 151 = - 7.4969±0.0020 (x 10 -4 )β, gI 153 = - 3.3125±0.0030 (x 10 -4 )β. In order to fit the measured line positions to the spin Hamiltonian which is usually assumed for the system it was necessary to add small higher-order terms. The results of these measurements are compared with the precise atomic beam measurement on Eu.