Response theory calculations of the singlet–triplet transition probabilities in the HOCl molecule

Abstract

The role of the HOCl molecule in stratospheric photochemistry is highly dependent on its photolysis in the long wavelengthregion (λ 300 nm). In order to predict the possible importance of the singlet–triplet absorption in this molecule we haveperformed geometry optimizations of the ground singlet X¹A′ and the excited triplet ³A″ and ³A′ states, and performed quadraticresponse theory calculations of the singlet–triplet transition probabilities at different bending angles and O–Cl distances, accounting for the complete form of the spin–orbit coupling operator. Based on the results of these calculations the importance of the ³A″ ← X¹A′ and ³A′ ← X¹A′ absorption in HOCl photolysis is discussed.