The absorption spectrum of SiO has been observed down to 250 Angstrom. Besi
des the Rydberg series reported by M. A. Baig and J. P. Connerade (1979, J.
PhYs. B: At. Mol. Ph ' vs. 12, 2309-2318), three new groups of Rydberg ser
ies have been observed converging at 18.59, 22.64, and 37.07 eV. These new
limits are compared to theoretical calculations (K. L. Cai and J. P. Franco
is, 1999, . Mol. Spectrosc. 197, 12-18) and to the isovalent molecule CO. (
C) 2001 Academic Press.