Dissociative electron attachment near threshold, thermal attachment rates, and vertical attachment energies of chloroalkanes

Abstract

The peaks appearing near zero energy in the dissociative electron attachment cross section of 18 chloroalkanes are studied by electron beam methods. Fits to the experimental data are made using model cross sections having appropriate energy dependences and inclusion of the broadening due to the electron energy distribution. The magnitudes of the zero peaks are found to be well correlated with the vertical attachment energies ͑VAE͒ associated with occupation of the lowest empty orbitals of the compounds. The magnitudes rise exponentially by more than five orders of magnitude as VAE decreases from 2 eV to a slightly negative value. This dependence is a consequence not only of the thermal population of vibrational levels, but also of an approximately linear relationship between VAE and the energy of the crossing between the neutral and anion potential curves. Franck-Condon factors for the transition to the anion curve are computed for model potential curves, and the nature of the attachment from vibrational levels with energies near that of the crossing point is explored in a local potential resonance picture. A substantial contribution arises from tunneling to the anion state from vibrational levels below the barrier. Thermal attachment rate constants are also computed from our data. These are also shown to vary exponentially with VAE.

Electron attachment to chlorinated alcohols

“…The rate constant for the thermal electron capture strongly depends on the extent of overlap between the shape and position of the dissociative electron attachment (DEA) cross-section peak and the Maxwell-Boltzmann distribution of both electron and molecules energies [15,16,17].…”

Temporary anion states and dissociative electron attachment to nitrobenzene derivatives

“…However, a model of these processes with predictive power has not yet been developed. DEAS and NIMS, closely connected with the ETS technique [5,10], give information on the dissociative decay channels which follow electron attachment. The DEA cross section σ DA (E) may be represented as the product of a capture cross section σ Cap (E) and the anion survival factor ρ [10,11], where E is the electron impact energy:…”

Dissociative electron attachment to methyl chloride: A quasi-diatomic potential curve for the fragmentation of the metastableCH3Cl-anion

“…This is in strong contrast to most other chemical reactions. Electron attachment to CH 3 Cl has been the subject of many experimental studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] performed both by swarm and beam techniques. Cross-sections for the formation of anions, thermal attachment rates as well as resonance energies and widths have been measured in these experiments.…”