In a quantum dot made of an indirect gap material such as Si, the electron-
hole Coulomb interaction alone can give rise to "dark" excitons even in the
absence of exchange interaction. We present the predicted excitonic spectr
a for hydrogen-passivated Si dots and find very good agreement with the rec
ent experiment of Wolkin, Jorne, Fauchet, Allan, and Delerue [Phys. Rev. Le
tt. 82, 197 (1999)]. The calculated splitting between dark and bright excit
ons, arising from Coulomb and exchange interactions, agrees very well with
the optical data of Calcott, Nash, Canham, Kane, and Brumhead [J. Phys Cond
ens. Matter 5, L91 (1993)]. (C) 1999 American Institute of Physics. [S0003-
6951(99)04845-7].