The energy loss of H-3(+)-molecule beams interacting with amorphous ca
rbon targets has been calculated, both as a function of the target thi
ckness and the projectile velocity. We have considered the spatial cha
nges, due to Coulomb repulsion, of the initial molecular configuration
after the H-3(+) ion enters the target and then used a dielectric for
malism to evaluate the stopping power of the correlated protons. The r
atio between the stopping power of the H-3(+) molecule and that of its
constituents considered individually accounts for the vicinage effect
s and agrees reasonably well with available experimental data.