  Transition operator method is proposed for description of the dynamics of
spectroscopic transitions. Quantum-mechanical analogue of Landau-Lifshitz
equation has been derived for the system representing itself the periodical
ferroelectrically (ferromagnetically) ordered chain of $N$ equivalent elements,
interacting with external oscillating electromagnetic field. Landau-Lifshitz
equation was represented in Lorentz invariant form by using Hilbert space over
the ring of quaternions. It has been shown, that spin vector can be considered
to be quaternion vector of the state of the system studied. From comparison
with experiment for the first time from pure optical measurements the value of
spin $S = 1/2$ for optically active centers - spin-Peierls solitons in carbon
chains - has been obtained. The ratio of imagine to real components of complex
charge is evaluated for given centers to be $\frac{g}{e} \approx (1.1 -
1.3)10^{2}$.
