CARS thermometry in a transversely heated graphite-tube atomizer used in atomic absorption spectrometry

Abstract

An experimental setup for gas-temperature diagnostics using Coherent Anti-Stokes Raman Scattering (CARS) in very small sample volumes with great spatial and temporal temperature variations is presented. Studies have been started of a newly designed transversely heated graphite-tube atomizer for atomic absorption spectrometry (Perkin-Elmer, 4100 ZL). For the investigations, high spatial resolution and precise time synchronization of the measurements and also automatic control of the time-dependent intensity of the anti-Stokes signal were realized. The graphite-tube atomizer also offers the possibility of high-temperature-gas spectroscopy. A high-temperature CARS spectrum of CO₂, recorded in the graphite tube at 2300 K, is shown for the first time. A number of hot-band transitions in the spectral region of the Fermi doublet at a Raman shift from 1230 to 1450cm⁻¹ was observed and assigned, making possible the use of CO₂ as “spectroscopic thermometer gas”, similar to N₂.