We investigate the isotopic variation of the (C) over tilde -state absorption spectrum of sulfur dioxide (SO2). Low-lying vibrational energy levels of four isotopomers were obtained using the Lanczos method on a recent ab initio potential energy surface of the (C) over tilde -state of SO2. The corresponding absorption spectra up to 185 nm were determined using a Chebyshev method with ab initio transition dipole functions. Implications for the recently observed mass-independent isotope effects are discussed. (C) 2007 Elsevier B.V. All rights reserved.