9.8 The rate theory of unimolecular reaction 9.8.2 Christiansen and Lindemann's consideration (1)Special consideration In 1921. Christiansen postulated that the activation of molecules in unimolecular reaction is also through intermolecular collision For this theory, it is easy to explain the second-ordered feature of unimolecular reaction at low pressure but it is impossible to gave any reasonable explanation to its first-ordered feature at high pressure In 1922 Lindemann and Christiansen postulated that the activated molecules react long after the collision. There is a time lag between activation and reaction. During the stay of activated molecules, some of them may lose their energy due to the further collision( deactivation). Only part of the activated molecules form productIn 1921, Christiansen postulated that the activation of molecules in unimolecular reaction is also through intermolecular collision. For this theory, it is easy to explain the second-ordered feature of unimolecular reaction at low pressure but it is impossible to gave any reasonable explanation to its first-ordered feature at high pressure. In 1922 Lindemann and Christiansen postulated that the activated molecules react long after the collision. There is a time lag between activation and reaction. During the stay of activated molecules, some of them may lose their energy due to the further collision (deactivation). Only part of the activated molecules form product. 9.8.2 Christiansen and Lindemann’s consideration (1) Special consideration 9.8 The rate theory of unimolecular reaction