Subpicosecond time-resolved absorption spectra were recorded, in the visible and near-infrared regions, for the LH2 antenna complexes from Rhodobacter sphaeroides G1C, Rhodobacter sphaeroides 2.4.1, Rhodospirillum molischianum, and Rhodopseudomonas acidophila. The efficiencies of carotenoid-to-bacteriochlorophyll singlet-energy transfer through the 1(1)B(u)(+), 1(1)B(u)(-), and 2(1)A(g)(-) channels in the LH2 complex were determined to be 48%, 19% and 22% in Rhodobacter sphaeroides G1C; 46%, 18% and 20% in Rhodobacter sphaeroides 2.4.1; 48%, similar to2% and similar to1% in Rhodospirillum molischianum; and 48%, similar to2%, similar to4% in Rhodopseudomonas acidophila. Sums of efficiencies through the three channels in the four LH2 complexes, 88%, 84%, 51% and 54%, nicely correlate with the efficiencies that were determined by comparison of the absorption and fluorescence-excitation spectra, 92%, 89%, 53% and 56%. (C) 2004 Published by Elsevier B.V.