Imaging ion-molecule reactions: Charge transfer and C-N bond formation in the C+ + NH3 system

Abstract

The velocity mapping ion imaging method is applied to the ion-molecule reactions occurring between C(+) and NH(3). The velocity space images are collected over the relative collision energy range from 1.5 to 3.3 eV, allowing both product kinetic energy distributions and angular distributions to be obtained from the data. The charge transfer process appears to be direct, dominated by long-range electron transfer that results in minimal deflection of the products. The product kinetic energy distributions are consistent with a process dominated by energy resonance. The kinetic energy distributions for C-N bond formation appear to scale with the total available energy, providing strong evidence that energy in the [CNH(3)](+) precursor to products is distributed statistically. The angular distributions for C-N bond formation show pronounced forward-backward symmetry, as expected for a complex that resembles a prolate symmetric top decaying along its symmetry axis.

The Selective Role of Long‐Range Forces in the Stereodynamics of Ion–Molecule Reactions: The He++Methyl Formate Case From Guided‐Ion‐Beam Experiments

“…[24] Ion-molecule reactions that have been studied in such detail are still limited, relativelys parse andi nm ostc ases confined to simple systemsw ith as mall number of atoms (for recente xamples, see refs. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]). …”

Imaging ion-molecule reactions: Charge transfer and halide transfer reactions of O+ with CH3Cl, CH3Br, and CH3I

“…As noted in our other publications [20,32,33], the kinetic energy distributions in charge transfer mirror the distributions of internal states consistent with the Franck-Condon factors connecting the neutral reactant and its ion [34,35]. The low energy photoelectron spectra of methyl halides provide some insight on this point: the spectra generally show a weakly structured band near threshold, consistent with Franck-Condon activity in the CÀ ÀX stretch of the methyl halide [36].The product angular distributions obtained by integrating the velocity space distributions over recoil speed may be calculated according to Eq.…”

“…As described previously [20], resonant charge transfer between an ion beam of Ar + and a neutral beam of Ar produced by supersonic expansion is employed to establish a velocity marker at thermal velocity, corresponding to a lab energy of 0.064 eV. Coupled with direct measurement of the ion beam energy distribution with an electrostatic energy analyzer, these measurements result in a velocity scale that is accurate to AE0.2 Â 10 2 m s À1 .…”

“…As described previously [20], the experiment is performed with a crossed beam instrument equipped with a velocity map imaging (VMI) detector [17]. The imaging system measures all product velocities for a given mass in a single detection time interval.…”

Ion imaging study of dissociative charge transfer in the N2+ + CH4 system

“…As described in a previous publication, 13 the kinematics of resonant charge transfer between an atomic beam of Ar + and a neutral beam of Ar produced by supersonic expansion are employed to establish a velocity marker at thermal velocity, or 5.54 × 10 2 m s −1 under our operating conditions, corresponding to a lab energy of 0.064 eV. Coupled with direct measurement of the ion beam energy distribution, these measurements result in a velocity scale that is accurate to ± 0.2 × 10 2 m s −1 .…”