Spectral diffusion tunneling two-level systems

An investigation is made of spectral diffusion due to flip-flop processes in tunneling two-level systems. It is shown that at low frequencies ($\omega\ll2k_{\textup{Б}}T/\hbar$) of the pulses that saturate the state of the two-level systems and at low temperatures ($T<1\,\textup{K}$) the mechanism of excitation energy transport through the spectrum of the systems due to flip-flop processes is effective.