The rate constant of the disproportionation channel 1a of the self-reaction of hydroxyl radicals OH + OH H 2 O + O (1a) was measured at ambient temperature as well as over an extended temperature range to resolve the discrepancy between the IUPAC recommended value (k 1a = 1.48x10 -12 cm 3 molecule -1 s -1 , discharge flow system, Bedjanian, Y.; Le Bras, G.; Poulet, G.