Isotope selective IR multiphoton dissociation in an efficient laser waveguide reactor

Abstract

Isotope selective IR multiphoton dissociation (MPD) was investigated in a simple Pyrex glass waveguide (WG) reactor. Important theoretical and experimental studies were performed concerning the excitation-dependent transmission properties of the WG with a transverse electric atmosphere (TEA) CO₂ laser. From these studies, the WG parameters can be selected for efficient MPD. Various important aspects such as laser beam quality excitation of various WG modes, beam coupling in the WG and wall-induced breakdown or reaction, etc. are discussed. The WG reactor was initially operated with well-known systems such as SF₆ and CF₃Br. The dissociation yield was several times larger than that obtained with a conventional cylindrical reactor, whereas the separation factor remained unchanged. Therefore the WG reactor can be used for isotope selective dissociation and the process parameters can be determined using fewer laser pulses even in a poor absorptive medium. Using this reactor, we report, for the first time T-D separation in CTF₃-CDF₃ mixtures by exciting at the wings of CTF₃ absorption. Optimization of these reactors will eventually lead to a better utilization of laser photons and the reactor may then be integrated into full-scale separation plants.