We report differential conductance measurements through a double quant
um dot with adjustable interdot tunneling rate. The Coulomb gap of the
double dot decreases continuously as the interdot tunnel conductance
G(int) is increased, from the gap of two isolated dots (when G(int)sim
ilar to 0) to the gap of a single large dot of twice the total capacit
ance (when G(int) = 2e(2)/h). Excited electronic states in differentia
l conductance measurements on single dots show a spectrum which is ess
entially independent of the number of electrons in the dot, but is not
uniform. (C) 1997 American Institute of Physics.