Formula_755

\[\begin{gathered}a_{k}(t)=a_{k}\left(t_{0}\right) \exp \left\{-i \omega_{k}\left(t-t_{0}\right)\right\}-i m_{k}^{+}(t), \\m_{k}^{+}=\int_{t_{0}}^{t} \exp \left\{i \omega_{k}(\tau-t)\right\} M_{k}^{+}(\tau) d \tau,\end{gathered}\]