Since they are impossible to isolate, they are very difficult to study; femtochemical IR spectroscopy, however, can provide a useful approximation of their structure.
Since they are impossible to isolate, they are very difficult to study; femtochemical IR spectroscopy, however, can provide a useful approximation of their structure. These are identified by the coordinates of the saddle points of the potential energy surface and hypothesized in arrow-pushing reaction mechanism diagrams. Although they are absent in phase transitions, the instability and high energy of these  configurations gives plots of potential energy versus reaction coordinates their characteristic hill-shaped appearance. E to the power of the opposite of the energy of these minus the energy of the products divided by the universal gas constant times the absolute temperature gives the rate constant, and that energy is known as the Arrhenius or activation energy. Also known as activated complexes, FTP name this high-energy molecular configuration found between reactants and products—and between those and chemical  intermediates.
Since they are impossible to isolate, they are very difficult to study; femtochemical IR spectroscopy, however, can provide a useful approximation of their structure.
transition states (accept activated complexes before named)