Spectroscopic investigation of the response of the NO2-N2O4 chemical system to optical laser pumping

An argon laser beam was used to perturb the NO₂-N₂O₄ chemical system. The perturbation was monitored, in different experiments, with the laser-induced fluorescence and the IR optical double-resonance (IODR) techniques. The expected quantum perturbations which involve specific rotational levels in NO₂, $\text{X}$ ²A₁ were observed. Unexpected chemical effects which involve the ground state concentration of both species and which are attributed to the response of the chemical equilibrium to the optical perturbation were also observed. The IODR results are discussed with the help of a model based on the Beer-Lambert law, which allows the role of the chemical response to be demonstrated.