Homogeneous nucleation of a vapor in the presence of the loss of clusters by diffusion and
thermophoretic drift is investigated. Analytical results are obtained for the cluster size
distribution and the rate of nucleation by solving the modified kinetic equation for nucleation.
The implications of cluster loss by diffusion and phoretic drift on the onset of the homogeneous
nucleation of silicon vapor in the horizontal epitaxial chemical vapor deposition reactor is
discussed. The range of conditions under which the loss of subcritical clusters by diffusion and
drift becomes important for the interpretation of diffusion cloud chamber experimental data of
the onset conditions of the homogeneous nucleation of vapors is also delineated
