Theory of paramagnetic acoustic resonance absorption by U4+ ions in cubic crystalline field

Ultrasonic paramagnetic resonance absorption coefficients by f2 ions in a cubic field are calculated with special reference to U4+ in ThO2. The UPR absorption coefficients at liquid helium temperature are large and comparable in magnitude to those of lanthanide ions with an even number of electrons, however they drop very rapidly with the elevation of temperature. The tetragonal and the trigonal coupling constants, A0 and B0, in the orbit-lattice interaction Hamiltonian can be determined independently by measuring the absorption coefficients with longitudinal and transverse waves, respectively. The characteristic angular dependences of absorption coefficients are also discussed. (auth.)