COLLISION INDUCED INTENSITIES OF SINGLET-TRIPLET AND COOPERATIVE TRANSITIONS IN A SIMULATED SYSTEM $O_{2}+ C_{2}H_{4}$. CALCULATED BY Cl APPROACH

Abstract

Author Institution: Cherkassy Technological InstituteCollision complex between molecular oxygen and ethylene was calculated by CI approach in 6-31 $G^{\ast}$ basis set, scanning the intermolecular distance, R, in $C_{2v}$ symmetry of collision (C=C and O-O bands are parallel). The system simulates conditions, in which a great enhancement of ethylene singlet-triplet absorbtion was observed at high oxygen pressure. The triplet ground state ($X^{3} \Sigma^{-}{_{g}}lA_{g}$) of the complex and low lying singlet states $(a^{1} \Delta g$ and $b^{1} \Sigma^{-}{_{g}}$ oxygen states in collision with ground state of ethylene, $^{1} \Delta_{g}$) have small dissociation energies, $D_{e}$ (an order of $0.4 kJ/mol, R_{e} = 3.8$ A); the Herzberg states ($A^{\prime 3} \Delta_{u} 1Ag$) have large splitting and $De = 3.3$ kJ/mol for the lowest term at $R_{e} = 3$ A. Ethylene excited $\pi \pi^{\ast}$ singlet state $(^{1}B_{1u}$) in contact with $O_{2}(X^{3} \Sigma^{-}{_{g}}$) exibits very stable eximer feature, because of large charge transfer admixture. By the same reason the triplet-singlet transition between plane $\pi \pi^{\ast}$ states of ethylene moiety, induced by collision with molecular oxygen has enormous large electric dipole moment (0.41 $ea_{o}$ at $R = 3.2$ A). The observed transitions intensities are in a reasonable agreement with CI results. The UV band (260 nm) correspons to $X^{3} \Sigma^{-}{_{g}} - A^{3} \Delta_{u}$ transition, highly enhanced by collision (instead of earlier proposed $X^{3} \Sigma^{-}{_{g}} - A^{3} \Sigma^{+}{_{u}}$ transition)