The interaction of excited He, Ar and Ne metastable atoms with the CF₂Cl₂molecule

Abstract

We studied Penning ionization of the CF2Cl2 molecule by neon and helium metastable atoms. In the case of the neon ionizing particle, we measured the electron kinetic energy as well as mass spectra; for helium metastable atoms, only the mass spectrum was recorded. We, therefore, obtained the branching ratios for the heavy charged particles produced in both interactions. In this report we will discuss the mechanism involved in the production of metastable halogen atoms in the dielectric barrier discharge further to the use of rare gases/CF2Cl2 mixtures. We show that this process needs a two-stage reaction. Ground state free halogen atoms are formed over the first stage by Penning ionization, charge transfer, dissociate excitation and ionization. Therefore, metastable halogen atoms can be produced by excitation transfer process in the second stage through interaction with metastable rare gas atoms.

Interaction of excited He and Ne rare gas metastable atoms with the CHF2Cl molecule

“…The preferential attack of He * towards chlorine can also be interpreted as resulting from the higher activity of this atom with respect to fluorine. We had previously observed a similar situation in our study of He * and Ne * interaction with CF 2 Cl 2 molecule [35]. A selective orientation of the colliding system can be related to the spatial extent of the molecular orbital concerned by ionization and to the polarizability of the ionizing particle.…”

“…For dissociation paths allowing production of CHF + 2 , CHFCl + and CF + fragments, we note the possibility of freeing a neutral ground state halogen atoms. Under plasma reactor conditions, these atoms may interact, in a second stage, with the excited rare-gas atoms to produce Cl * /F * ( 4 P j ) species as we discussed in the last paper [35]. In our apparatus, which is based on the crossing beam principle, such a reaction is not favoured due to the great density of the CHF 2 Cl molecule at the inlet of the gas nozzle where the interaction takes place.…”

Deep core ionic photofragmentation of the CF2Cl2 molecule

“…Several studies have been dedicated to the photoabsorption and dissociation of the CF 2 Cl 2 molecule, both in the valence and in the inner-shell regions [5,[7][8][9][10][11][12]. Fragment ions produced from the CF 2 Cl 2 molecule photoexcited in the soft X-ray region have been measured from 44 to 1200 eV by Suzuki et al [5].…”

“…The main structural parameters of CF 2 Cl 2 ions as well as effective atomic charges and energies required for activating different dissociation channels have also been calculated. Cherid et al studied Penning ionization of the CF 2 Cl 2 molecule by Ne and He metastable atoms [11]. They obtained the branching ratios for the heavy charged particles produced and discussed the mechanisms involved in the production of metastable halogen atoms.…”