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 transition in oxygen molecules. The molar absorption coefficient (₁₂₇₃) 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.