Tetracene oxygenation caused by infrared excitation of molecular oxygen in air-saturated solutions: the photoreaction action spectrum and spectroscopic parameters of the transition in oxygen molecules

The action spectrum of tetracene photooxygenation was measured in air-saturated carbon tetrachloride in the wavelength range of 1220–1290 nm using a wavelength-tunable forsterite laser. The data show that the photoreaction occurs due to laser excitation of the 1 Δ g ( ν = 0 ) ← 3 Σ g - ( ν = 0 ) transition in oxygen molecules. The molar absorption coefficient (ϵ1273) and the cross section of light absorption (σ1273) corresponding to the spectral maximum of this transition were calculated from the observed photoreaction rates. The obtained values ε1273 = 0.003 M−1 cm−1 and σ1273 = 10−23 cm2 (±20%) reasonably correlate with those extrapolated from the high-pressure oxygen absorption spectra.