  We introduce a path sampling method for the computation of rate constants for
systems with a highly diffusive character. Based on the recently developed
algorithm of transition interface sampling (TIS) this procedure increases the
efficiency by sampling only parts of complete transition trajectories confined
within a certain region. The algorithm assumes the loss of memory for highly
diffusive progression along the reaction coordinate. We compare the new
technique to the TIS method for a simple diatomic system and show that the
computation time of the new method scales linearly, instead of quadraticaly,
with the length of the diffusive barrier. The validity of the memory loss
assumption is also discussed.
