H. LIU, E. C. LIM, Department of Chemistry, University of Akron, Akron, Ohio 44325-3601; C. MUNOZ-CARO, A. NINO, E. U. Inform\acuteatica, Universidad de Castilla-La Mancha, Ronda de Calatrava 5, 13071 Ciudad Real, Spain; R. H. JUDGE, Department of Chemistry, University of Wisconsin-Parkside, Kenosha, WI 53141-2000; D. C. MOULE, Department of Chemistry, Brock University, St. Catharines, Ontario, Canada, L2S 3A1 .

Acetaldehyde molecules in the first singlet excited state contain two coupled low frequency vibrational modes, ₁₄ (inversion) and ₁₅ (torsion). In an earlier paper, \footnoteH. ~Liu, E.~C.~Lim, C.~Munoz-Caro, A.~Nino, R.~H.~.Judge and D.~C.~ Moule,~J.~Mol.~Spectrosc., 175, 172-189 (1996). a two dimensional least squares analysis of the first seven bands in the UV spectrum of acetaldehyde jet-cooled vapor gave an excited state barrier to inversion of 585.13 cm^-1 and a torsional barrier of 721.43 cm^-1. A discussion of the results of a vibrational and rotational analysis of 12 additional bands beyond this earlier analysis will be presented. The assignment of the 14²₀ band has changed and the inclusion of the higher members of the torsional mode has given refined values for the barriers.