  Kinetics of collapse and explosion transitions in microcanonical
self-gravitating ensembles is analyzed. A system of point particles interacting
via an attractive soft Coulomb potential and confined to a spherical container
is considered. We observed that for 100--200 particles collapse takes $10^3$ --
$10^4$ particle crossing times to complete, i. e., it is by 2-3 orders of
magnitude slower than velocity relaxation. In addition, it is found that the
collapse time decreases rapidly with the increase of the softcore radius. We
found that such an anomalously long collapse time is caused by the slow energy
exchange between a higher-temperature compact core and relatively cold diluted
halo. The rate of energy exchange between the faster modes of the core
particles and slower-moving particles of the halo is exponentially small in the
ratio of the frequencies of these modes. As the softcore radius increases, and
the typical core modes become slower, the ratio of core and halo frequencies
decreases and the collapse accelerates. Implications to astrophysical systems
and phase transition kinetics are discussed.
