Laser induced grating spectroscopy (LIGS) has been used to determine temperatures in the products of flames with high precision. The technique uses a pulsed beam at 1064 nm to excite weak water molecule lines to produce a density grating and an associated pressure pulse. The resulting density pattern is probed using a continuous wave laser.
The particular advantages of the 1064 nm LIGS are :
- the very high precision which arises from the measurement of a frequency.
- easily available excitation line with high energies from Nd:YAG lasers
- can be used to excite electrostrictive modes to obtain temperatures in reactants or products
The current version of the technique offers suffcient signal from 3 bar upwards for measurement of product temperatures.