The logistic map at r = 4 is modified in a narrow interval, stabilizin
g a low-period unstable periodic orbit and generating transient chaos.
The cumulative separation Delta between closely lying orbits is propo
rtional to their initial separation epsilon for epsilon < epsilon(c),
while for epsilon > epsilon(c) it is scattered within a band with epsi
lon-independent average, where epsilon(c) is a critical vaIue of initi
al separation. The pattern of (epsilon, Delta)-diagram is proposed for
characterization of transient chaos. On the basis of these considerat
ions, the concept of the uncertainty exponent is extended to the case
of transient chaos. (C) 1997 Elsevier Science B.V.