Speed-dependent line profile: A test of a unified model from the Doppler to the collisional regime for molecule-molecule collisions

A speed-dependent line profile combining soft and hard fully correlated Dic ke-narrowing collisions was recently successfully tested on Ar-broadened H- 2 spectra in a wide density and temperature range. A further test for mixtu res of H-2 in nitrogen molecules (instead of Ar atoms) is presented. This t est is also based on high resolution Raman investigation of the isotropic Q (1) line of H-2 from low to high density at various temperatures. The same consistency of the speed-dependent line profile as for H-2-Ar is obtained f or H-2-N-2 through a remarkable agreement with all the data by using a uniq ue set of four parameters (the collisional width and shift, the kinetic fre quency, and a characteristic velocity memory parameter). The present study is a preliminary step for the hydrogen CARS thermometry in H-2-air flames a t high pressure. (C) 2000 American Institute of Physics. [S0021-9606(00)015 33-6].