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=== Combined interactions ===
If there is a magnetic and electrical interaction at the same time on the radioactive nucleus as described above, combined interactions result. This leads to the splitting of the respectively observed frequencies. The analysis may not be trivial due to the higher number of frequencies that must be allocated. These then depend in each case on the direction of the electric and magnetic field to each other in the crystal. PAC is one of the few ways in which these directions can be determined.
=== Dynamic interactions ===
If the hyperfine field fluctuates during the lifetime <math>\tau_n</math> of the intermediate level due to jumps of the probe into another lattice position or from jumps of a near atom into another lattice position, the correlation is lost. For the simple case with an undistorted lattice of cubic symmetry, for a jump rate of <math>\omega_s<0.2\cdot \nu_Q</math> for equivalent places <math>N_s</math>, an exponential damping of the static <math>G_{22}(t)</math>-terms is observed:
:<math>G_{22}^{dyn}(t)=e^{-\lambda_d t}G_{22}(t)</math> <math>\lambda_d=(N_s-1)\omega_s
</math>
Here <math>\lambda_d</math> is a constant to be determined, which should not be confused with the decay constant <math>\lambda=\frac{1}{\tau}</math>. For large values of <math>\omega_s</math>, only pure exponential decay can be observed:
:<math>G_{22}^{dyn}(t)=e^{-\lambda_d t}
</math>
The boundary case after Abragam-Pound is <math>\lambda_d</math>, if <math>\omega_s>3\cdot\nu_Q</math>, then:
:<math>\lambda_d\approx\frac{2,5\nu_Q^2}{N_s\omega_s}
</math>
=== General theory ===
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