DISTINGUISHING THE FORMATION OF C2D4-2 LOSS) AND FROM C2D5H+ (BY HD LOSS) IN A REFLECTRON SPECTROMETER( IONS FROM C2D6+ (BY D)

The D-2 loss from C2D6+ ions and the HD loss from C2D5H+ ions has been investigated in a photoelectron photoion coincidence experiment emplo ying a reflecting ion time of a flight mass spectrometer (Reflectron). The experiment is able to distinguish the metastable formation of C2D 4+ ions (m/z = 32) from C2D6+ ions by D-2 loss and from C2D5H+ ions by HD loss simultaneously in a mixture of deuterated ethanes. The breakd own curves of the title reactions are presented and compared to the H- 2 loss from C2H6+ ions. The HD loss from C2D5H+ is Shifted by 67 meV a nd the D-2 loss from C2D6+ is shifted by 108 meV with respect to the H -2 loss from C2H6+. This shift reflects a strong kinetic isotope effec t which is most likely due to tunneling of H/D atoms through a barrier . (C) 1998 Elsevier Science B.V.