In the CORR experiments, H2 was always being produced, generating [H2]+ ions and H+ fragments, allowing them to function as the reagent ions (i.e., MH n(𝑛≥1) in Equation ( ) is H2, where M represents element H and n=1, A in Equation ( ) is H2 as well in this case). Therefore, both mechanisms are possible. Specifically, the abundant analyte molecules in the system, H2, H2O, and CO are able to collide with [H2]+ (through the proton transfer mechanism by transferring one of its H to the other molecule) or H+ ions (through the adduct formation mechanism by directly adding to the other molecule). This will allow for the generation of [H2+H]+, [H2O+H]+, and [CO+H]+ ions at M3, M19, and M29, respectively, as observed in Figure .