Mechanism of the cooperative vibronic emission of1δg singlet oxygen in solutions

The mechanism for inducing the probability of the¹_g-X³_g^– transition in an oxygen molecule with the simultaneous excitation of a vibration state of the solvent has been considered. The intensification of the 0-0 band of this transition under the influence of the solvent is attributed to the induction of the electric dipole moment of the b¹_g⁺-¹_g (m_ba) transition during a collision between O₂ and solvent molecules. It has been shown that m_ba is strongly dependent on the intermolecular distance and, consequently, on the normal coordinate of the vibrations of the solvent (Q) at a given collision parameter. Calculation of the derivative m_ba/Q (with consideration of the strong spin-orbit coupling of the b¹_g⁺ and X³_g^– states) makes it possible to account for the intensity of the new luminescence band of¹_g singlet oxygen, which is shifted toward longer wavelengths relative to the 0-0 band of the¹_g-X³_g^– by the value of the vibrational quantum of the solvent.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 594–596, September–October, 1985.