Spectral and Temperature Dependence of Laser Induced Dissociative Attachment in SF6

R Barbe,A Lagreze,J.-P Schermann,J.-P Astruc

doi:10.1155/lc.1.17

Abstract

We consider the influence of resonant laser excitation upon the dissociative reaction between SF6 molecules and very low energy electrons. Experimentally, the use of valence electrons of atoms in Rydberg states ensures a well‐defined energy resolution of the scattering electrons in the crossed beam apparatus. A spectroscopic model of the infrared absorption of CO2 laser radiation by SF6 gives a fair determination of the energy levels and vibrational transitions involved in the dissociative process. This reaction between highly excited atoms and a molecule is interpreted as a three step process: attachment of a quasi‐free electron, followed by the interaction between the atomic ionic core and the negative molecular ion leading to a partial stabilization and, finally, the competition between the dissociating and the autodetachment channels.

Highlights

The multiple photon dissociation (MPD) of SF6 into neutral components occurs in two stages, one involving a resonant excitation of the first few discrete vibrational states of the v3 ladder, the other leading to dissociation by absorption of a large number of photons within the vibrational quasicontinuum
The large amount of nonresonant laser energy which is required in the second step of the MPD dissociation into neutral components is replaced by chemical energy, i.e. the electron affinity of the
We consider here a reaction between SF6 molecules excited with 3 10 vibrational quanta, and very low energy electrons

Summary

Introduction

The multiple photon dissociation (MPD) of SF6 into neutral components occurs in two stages, one involving a resonant excitation of the first few discrete vibrational states of the v3 ladder, the other leading to dissociation by absorption of a large number of photons within the vibrational quasicontinuum. An alternative approach to isotopically selective dissociation of SF6 has been proposed and studied by several authors.[2] In this approach, one takes advantage of a well-known property of SF6: it attaches low energy electrons and, according to its vibrational energy, the negative ion produced R. The resonant vibrational excitation can strongly modify the branching ratio between the non-dissociative and dissociative channels [Figure 1]. The large amount of nonresonant laser energy which is required in the second step of the MPD dissociation into neutral components is replaced by chemical energy, i.e. the electron affinity of the SFs product

Results

Discussion

Conclusion