Dissociative attachment to excited SF6: selective IR excitation versus thermal activation

IR photon enhanced dissociative electron attachment to SF6: Dependence on photon, vibrational, and electron energy

“…Moreover, they found a substantial isotope effect with the photon-induced yield for 34 SF À 5 production being optimal on the 10P44 line near 920 cm À1 . Recent similar work by Rosa et al [17] confirmed the results of Chen and Chantry. Rosa et al proposed that in the framework of localized potential energy surfaces the effect of the laser-excited m 3 mode on SF À 5 production at E % 0 eV is explained by the level of the curve crossing between the neutral and anionic system matching the energy of the m 3 vibration.…”

“…The shape of the DEA cross section was found to be strongly dependent on the gas temperature T G (i.e. on the internal rovibrational energy of the SF 6 target molecules), exhibiting a shift and a rise of the peak cross section towards zero energy with increasing T G [3,8,15,[17][18][19]. To account for these observations, the higher energy peak in SF À 5 production has been attributed to attachment into a repulsive potential surface and subsequent direct dissociation [8,11,12,18].…”

“…Several electron collision experiments involving SF 6 molecules, vibrationally excited by CO 2 laser lines, have been carried out earlier [8,17,[31][32][33][34][35]. Stricklett and Burrow [35] detected changes in the total electron scattering cross section at energies E = 0-14 eV, as induced by CO 2 laser excitation of SF 6 molecules in a free jet.…”

“…Towards higher energies (300 meV), the yield for SF À 6 formation strongly decreases by more than four orders of magnitude [3,18], and DEA yielding SF À 5 ions takes over with a peak maximum located between 0.3 and 0.6 eV [3,5,8,15,[17][18][19]. The shape of the DEA cross section was found to be strongly dependent on the gas temperature T G (i.e.…”

“…One of the most important properties of SF 6 is its high cross section for the capture of low-energy electrons, forming predominantly long-lived SF À 6 ions by non-dissociative attachment and -towards higher energies -SF À 5 þ F by dissociative electron attachment (DEA) [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Although electron attachment to SF 6 has been studied over many years, several important aspects still need to be clarified.…”