AbstractCoherent anti‐Stokes Raman scattering (CARS) is a widely accepted standard for thermometry in combustion environments. Accurate lineshape models are of crucial importance for the computation of CARS spectra used for temperature and concentration evaluations. Therefore, a new lineshape model for the H2 molecule is developed and tested for ambient pressure applications. Measurements were taken in a heated cell and in a partially premixed flame with dual‐pump CARS techniques, respectively. Line broadening coefficients for H2N2 mixture are calculated using the new speed memory effects model. The experimental vibrational‐CARS (VCARS) spectra were evaluated with this new lineshape model and the temperature and relative H2 concentration results were compared with an already existing model. Copyright © 2009 John Wiley & Sons, Ltd.