Direct D-atom Incorporation in Radicals: An Overlooked Pathway for Deuterium Fractionation

Abstract Direct D-H exchange in radicals is investigated a quasi-uniform flow employing chirped-pulse millimeter-wave spectroscopy. Inspired by the H-atom catalyzed isomerization of C 3 H 2 reported our previous study, D-atom reactions with propargyl (C ) radical and its photoproducts were investigated. We observed very efficient enrichment through an analogous process D addition/H elimination to isomers occurring at 40 K or below. Cyclic HD only deuterated isomer observed, consistent expected addition/elimination yielding lowest energy product. The other product, propargyl, not directly detected, although presence inferred observations latter part flow. There, high-density region flow, we both isotopomers singly propyne attributed stabilization H+C D+C adducts. implications these for deuterium fractionation hydrocarbon astrochemical environments discussed support monodeuterated chemical kinetic model.