Transient absorption in 394-435 nm wavelength range following 193 nm photolysis of disilane has been measured by using cavity ring-down spectroscopy (CRDS). A broad and continuum absorption band was observed. Time profiles of the absorption measured at several wavelengths were similar and found to have at least two components. The decaying part of the absorption can be attributed to Si(H-2)Si based on the kinetic consideration and available information from the literature. The absorption was also measured in the hot wire CVD (HW-CVD) of SiH4. A broad and continuum band was observed. (C) 2007 Elsevier B.V. All rights reserved.