Raman spectrometer for high precision temperature sensing of atmospheric gases.

We present a highly accurate Raman spectrometer capable of measuring changes in atmospheric temperature as small as 0.75 K with high spatial and temporal resolution. The spectrometer is based on a laser diode tuned to the resonant absorption line of the isotope near 780.0 nm. A heated glass cell containing Rb atoms was used as an ultranarrowband atomic absorption notch filter with 0.3 bandwidth and optical density as high as four. This filter was placed in front of the spectrograph and blocked up to 99.99% of the elastically scattered laser light, which made it possible to resolve the pure-rotational Raman spectra of molecular atmospheric gases. The relative intensities of pure-rotational Raman transitions were then used to infer atmospheric temperature changes.