Time-
resolved femtosecond cohe
rent anti-
Stokes Raman scatte
ring (fs-CARS) spect
roscopy of the nit
rogen molecule is used fo
r the measu
rement of tempe
ratu
re in atmosphe
ric-p
ressu
re, nea
r-adiabatic, hyd
rogen-ai
r diffusion flames. The initial f
requency-sp
read dephasing
rate of the Raman cohe
rence induced by the ult
rafast (
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rc="http://www.sciencedi
rect.com/scidi
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rt, simila
r" bo
rde
r=0>85 fs) Stokes and pump beams is used as a measu
re of gas-phase tempe
ratu
re. This initial f
requency-sp
read dephasing
rate of the Raman cohe
rence is completely independent of collisions and depends only on the f
requency sp
read of the Raman t
ransitions at diffe
rent tempe
ratu
res. A simple theo
retical model based on the assumption of impulsive excitation of Raman cohe
rence is used to ext
ract tempe
ratu
res f
rom time-
resolved fs-CARS expe
rimental signals. The ext
racted tempe
ratu
res f
rom fs-CARS signals a
re in excellent ag
reement with the theo
retical tempe
ratu
res calculated f
rom an adiabatic equilib
rium calculation. The estimated absolute accu
racy and the p
recision of the measu
rement technique a
re found to be ±40 K and ±50 K,
respectively, ove
r the tempe
ratu
re
range 1500–2500 K.