Vibrational mode and collision energy effects on proton transfer in phenol cation–methylamine collisions

Abstract

Articles you may be interested inVibrational mode and collision energy effects on reaction of H 2 CO + with C 2 H 2 : Charge state competition and the role of Franck-Condon factors in endoergic charge transfer Vibrational and collisional energy effects in the reaction of ammonia ions with methylamine Mass-analyzed threshold ionization has been used to prepare vibrationally state-selected phenol cations, that were then reacted with methylamine at collision energies ranging from 0.1 to 2 eV. Integral cross sections and product recoil velocity distributions are reported. Ab initio calculations of stationary points on the surface and RRKM ͑Rice-Ramsperger-Kassel-Marcus͒ analysis of complex lifetimes are also presented for comparison. The only reaction observed over the entire energy range is exoergic proton transfer ͑PT͒. For ground-state reactants, the PT cross section is reduced by increasing collision energy, such that the reaction efficiency declines from ϳ71% at low E collision to ϳ50% at 2 eV. Excitation of either v 6a or v 12 vibrations inhibits reaction over the entire collision energy range, with the effect being somewhat mode-specific and increasing with increasing E collision . At low E collision , both vibrational and collision energy inhibit reaction with similar efficiency. Collision energy effects diminish at high E collision , while vibration continues to have a strong effect. Product ion velocity distributions are approximately forward-backward symmetric at E collision р1 eV, but are backward peaked at high energies. Mechanistic implications of these results are discussed.

Effects of Collision and Vibrational Energy on the Reaction of CH3CHO+(ν) with C2D4

“…There, too, density of states and adiabaticity factors tend to suppress the higher-energy charge state. We note that for all the polyatomic ion−molecule reactions we have studied we see CT only in cases where the endoergicity is less than 1 eV. ,,,− ,− For this system, the CT endoergicity is only 0.28 eV, hence the substantial CT cross section, but the PT−HT energy difference is 1.1 eV.…”

“…For the exoergic ME and HT reactions, the distributions are not significantly different for the reaction of vibrationally excited reactants. An absence of significant vibrational effects on recoil velocity is typical for exoergic reactions of polyatomic ions, 1,[15][16][17][18][19][20][21][22][23] and the reasons for the absence have been discussed recently. 24 The effects of vibration on the endoergic CT channel are discussed below.…”

“…We note that for all the polyatomic ion-molecule reactions we have studied we see CT only in cases where the endoergicity is less than 1 eV. 1,15,16,[18][19][20][21][22][23][24][32][33][34][35][36] For this system, the CT endoergicity is only 0.28 eV, hence the substantial CT cross section, but the PT-HT energy difference is 1.1 eV.…”

Effects of Bending and Bending Angular Momentum on Reaction of NO2+ with C2H2: A Quasi-Classical Trajectory Study

“…Finally, the experimental study found that NO 2 + vibrational excitation, particular bending, results in substantial changes in the product recoil dynamics at high collision energies, leading to a more forward-scattered velocity distribution than for the ground state. In past studies of vibrational effects on product recoil in ion reactions, we have seen insignificant effects on product recoil, even for reactions where vibration strongly affects reactivity. ,− Lack of vibrational effects on recoil is not surprisingenergy is likely to be scrambled in reactive collisions, and reactant E vib is typically only a small fraction of the total energy available to products, particularly at high E col . As might be expected, the exception has been for endoergic reactions near threshold, where E vib is a significant fraction of the energy available to products. , The present reaction is more than 2.5 eV exoergic, such that the bending vibrations contribute <3.5% of the available energy at high E col .…”

“…In past studies of vibrational effects on product recoil in ion reactions, we have seen insignificant effects on product recoil, even for reactions where vibration strongly affects reactivity. 5,[7][8][9][10][11][12][13][14][15][16][17] Lack of vibrational effects on recoil is not surprisingsenergy is likely to be scrambled in reactive collisions, and reactant E vib is typically only a small fraction of the total energy available to products, particularly at high E col . As might be expected, the exception has been for endoergic reactions near threshold, where E vib is a significant fraction of the energy available to products.…”