Autoionization process in the Penning ionization of the CO molecule by Ne∗ (3P0, 3P2) metastable atoms

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.

Section: Introductionmentioning

confidence: 99%

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

Cherid¹,

Arfa²,

Khodja³

2004

“…Otherwise the vibrational population will be greatly altered. This can happen when the ionization takes place via an excitation transfer process as has been previously observed in Ne * -CO 2 (Cermak 1976) and in Ne * -CO systems (Lescop et al 1996). Moreover Penning ionization can also occur via an ion-pair state.…”

Section: Introductionmentioning

confidence: 69%

Autoionization process in Penning ionization of the CO molecule by helium atoms in triplet metastable state

Lescop

Arfa

Cherid

et al. 1997

In this paper, we investigate the Penning ionization of the CO molecule by helium atoms in metastable states. The energy distribution spectrum of electrons related to the CO + (X 2 + ) ion state shows a deviation of the vibrational population from the predicted Franck-Condon factors. The angular distribution measurements exhibit an intensity increasing towards the backward direction for the v = 0 level, while the corresponding angular distributions of the higher vibrational levels (v = 2, 3 and 4) are isotropic. To explain these results, an excitation transfer process between the colliding particles is suggested. This gives rise to a CO molecule either in a doubly excited Rydberg state converging to CO + (D 2 ) or in the σ * quasi-bound state (shape resonance). Autoionization of the doubly excited state (CO * * ) leads to the population of vibrational levels which are forbidden by the Franck-Condon principle in the case of a direct processes.

“…For He * /Ne * -CHF 2 Cl systems, the energy of electron spectra was calibrated by adding a small amount of Ar to the target gas. No correction was made on the spectrometer transmission to take into account the slight variation of electron energy; indeed, previous studies carried out within our laboratory had evidenced the lack of significant change of electron energy over the present range (0-5 eV) [21][22][23]. It is worth noting that, usually, it is paramount to calibrate energy transmission prior to the measurement of electronic bands branching ratio.…”

Section: Methodsmentioning

confidence: 99%

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

Cherid

Arfa

Khodja³

2005

We studied the Penning ionization of the CHF2Cl molecule with He and Ne metastable atoms (He* and Ne*). We measured the electron kinetic energy and the time-of-flight mass spectra; we also determined the branching ratio for the parent ion and charged CHF+2, CHFCl+, HCF+/CF+ and Cl+ fragments. These data led us to discuss the dissociation channels for all the energetically-accessible electronic states of the ionized molecule. We evidenced a marked contrast in the fragment ion proportions for Ne*–CHF2Cl and He*–CHF2Cl systems, and related it to the difference in polarizability and internal energy of the He* and Ne* atoms.