S-branch CARS applicability to thermometry

The pressure and temperature dependence of background-free S-branch CARS spectra of N(2) are investigated in the temperature range of 300-700 K for pressures of 1-20 atm. Collisional narrowing for S-branch CARS spectra is proved to be negligible. Individual S-branch lines are clearly resolved in the entire range, enabling unequivocal determination of temperatures by their peak ratios. Advantages and disadvantages of S-branch CARS thermometry are discussed on the basis of experimental results. The dual narrowband Stokes CARS technique is also discussed as a practical method of S-branch CARS thermometry.