Detailed studies of flame-vortex interactions play a vital role in improving our understanding of turbulent combustion. A combined experimental and numerical study was conducted on a low-speed, buoyant, jet diffusion flame of hydrogen in air to investigate the vortex-flame interaction and the effects of preferential diffusion on the flame's structure. A time-dependent, axisymmetric mathematical model with detailed transport processes and a chemical-kinetics mechanism was used to Simulate the dynamics of the flame. Single-shot measurements of temperature and the concentrations of molecular hydrogen (H-2), the pollutant nitric oxide (NO), atomic oxygen (0), atomic hydrogen (H), and the hydroxyl radical (OH) were made using optical techniques such as coherent anti-Stokes Raman scattering, degenerate four-wave mixing, and planar laser-induced fluorescence. Temperature and mole fractions of different species are presented in two-dimensional contour maps and compared with the numerical predictions. The model predicted the behavior of the experimentally observed dynamic flame quite well, including variations in temperature and molar concentrations of fuel and tracer species such as H, OH, and NO. Discrepancies in the concentration of 0 atoms were also noted. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.