Photodissociation of vibrationally excited ozone

A two laser photodissociation technique has been used to measure the effect of ozone vibrational excitation on the cross section for photodissociative production of O(¹D) at several UV wavelengths in the Hartley band. Below the 310 nm energy threshold for the process, O₃+hν $\stackrel{\text{λ⩽310 nm}}{⟶}$ O₂(¹Δ_g)+O(¹D), vibrational excitation of O₃ was found to increase the cross section for production of O(¹D) by nearly two orders of magnitude. Substantial increases in both the O₃ photoabsorption cross section and the O(¹D) quantum yield were observed. Between the 310 nm threshold and the 255 nm absorption peak of the Hartley band, the effect of vibrational excitation was observed to decrease with increasing UV photon energy. The quantum yield of O(¹D) for photodissociation of unexcited, room temperature (300 °K) ozone was also measured to be Φ₀=0.15±0.07 at λ=314.5 nm.