The (A) over tilde(1)A" - (X) over tilde(1)A＇ spectra of jet-cooled HSiI and DSiI have been studied using the pulsed discharge technique, using H3SiI and D3SiI as precursors. The excited state vibrational frequencies have been determined and the literature value of v(1)＇ substantially revised. Although a reliable excited state equilibrium structure was unattainable, the rotational constants of the 0(0)(0) bands gave the structural parameters r(0)"(Si-I) = 2.463(1) Angstrom, r(0)"(Si-H) = 1.534(1) Angstrom, theta(0)"(HSiI) = 92.4(1)degrees, r(0)＇(Si-I) = 2.436(1) Angstrom, r(0)＇(Si-H) = 1.515(5) Angstrom, and theta(0)＇(HSiI) = 114.9(2)degrees. The radiative lifetime of the 0(0)(0) band has been measured to be 1230 +/- 30 ns. Trends in the,structural parameters, vibrational frequencies, and their changes on electronic excitation for the monohalosilylenes have been discussed.