 This confusion in the definition of PCET has led to the proposal of alternate names including electron transfer-proton transfer (ETPT), electron-proton transfer (EPT), and concerted proton-electron transfer (CPET).Also distinct is hydrogen atom transfer (HAT), in which the proton and electron start in the same orbitals and move together to the final orbital.HAT is recognized as a radical pathway, although the stoichiometry is similar to that for PCET.