  We measure the photoluminescence spectra for an array of modulation doped,
T-shaped quantum wires as a function of the 1d density n_e which is modulated
with a surface gate. We present self-consistent electronic structure
calculations for this device which show a bandgap renormalization which, when
corrected for excitonic energy and its screening, are largely insensitive to
n_e and which are in quantitatively excellent agreement with the data. The
calculation (cf. cond-mat/9908349) shows the importance of including
orthogonality between the screening electrons and the electron(s) bound to the
hole. The calculations show that electron and hole remain bound up to 3 x 10^6
cm^-1 and that therefore the stability of the exciton far exceeds the
conservative Mott criterion.
