Photodissociation of NOCl and NO2 in the Vacuum Ultraviolet

Abstract

AbstractThe photodissociation of NOCl and NO2 in the vacuum ultraviolet yields the electronically excited NO molecule which fluoresces in the near ultraviolet. The fluorescence spectrum, which lies mostly in the region 2200‐4000 Å, extends below 2200 Å as the wavelength of incident light decreases. This is interpreted in terms of the production of the NO C2Π, D2Σ+, B2Δ, E2Σ+ along with the production of the NO A3Σ+, B2Π. The fluorescence intensity and the yield have been measured as a function of incident wavelength. The fluorescence curves thus obtained are correlated with the absorption spectrum. The absorption coefficient of NOCl in the region 1100‐2200 Å has been measured. The absorption spectrum of NOCl between 1100 and 1700 Å may be divided into three regions, respectively, corresponding to transitions providing the NO A2Σ+, NO C2Π, D2Σ+ and NO B′2Δ, E2Σ+ with a simultaneous production of the ground state NO or other products. The absorption by NO2 in the spectral region from 1100‐1450 Å involves transitions yielding the NO A2Σ+, B2Π, NO C2Π, D2Σ and NO B'2Δ, E2Σ+ below their respective threshold wavelengths of incident light. Besides it has another transitions giving products other than the electronically excited NO. The threshold energy of the incident photon producing the NO A2Σ+ B2Π gives an upper limit of bond dissociation energy. The bond energies obtained are D(NO‐Cl) ≤ 1.77 ± 0.05 eV and D(NO‐O) ≤ 3.22 ± 0.05 eV which are 0.17 eV and 0.10 eV higher than the respective values obtained from the heat of formation.