  New experimental data of the comparative analysis of channels of the
production of three \alpha-particles and ^12C nuclei in ^16Op-collisions at
3.25 A GeV/c are submitted. It is shown, that the channel with the three
\alpha-particles production is realised in a half part of events as a result of
decay of an excited ^12C^* nucleus, and the rest part of the channel - by the
knocking-out of one \alpha-cluster from the weakly bound residual nucleus,
containing three \alpha-clusters. The modelling of the decay of an excited
system on the model of isotropic phase space is justified at small values of
excitation energy and, nevertheless, it allows to take the valuable additional
information about the dynamics of investigated process from experimental data.
