Selective multi-photon dissociation (MPD) of Freon-22 (CF 2 HCl) molecules has been carried out using a TEA CO 2 laser at various CO 2 laser lines (9P(20)-9P(26)) in order to maximize the yield of C-13 isotope in the product (C 2 F 4) at an enrichment factor of 100. The effects of laser pulse tail due to the presence of N 2 in the laser mixture on the enrichment factor and yield of C-13 are investigated. It is found that the addition of a small amount of N 2 is possible in the laser mixture without a significant drop in the yield at desired enrichment factor. Addition of a small amount of N 2 improves the laser efficiency considerably. At a given pulse energy, a slight change in the near field intensity distribution of a laser severely affects the selectivity of C-13 isotope. The computed far-field intensity distributions of the measured near-field intensities show marked spatial variation in the focal spots that leads to a drop in selectivity. For macroscopic production of C-13 isotope a simple and novel multi-pass cavity has been designed and tested to focus the energy repeatedly keeping the optimum fluence constant at each focal spot.

Multi-photon dissociation of Freon-22 (CF 2 HCl) at low temperatures has been carried out to separate the C-13 isotope using a TEA CO 2 laser. Yield and enrichment of C-13 isotope in the product C 2 F 4 are studied at 9P(22) laser line as a function of temperature (-50°C to 30°C). It is observed that at a given fluence when the temperature is lowered the yield decreases and the enrichment factor of C-13 increases. Room temperature irradiation of CF 2 HCl towards the blue edge of C-13 absorption (i.e. at 9P(20) laser line) gives low yield of the product (C 2 F 4) at a fluence, which produces the desired enrichment factor of 100. An increase in fluence gives very high yield of C 2 F 4 but the enrichment factor is very low. Irradiating CF 2 HCl at a temperature of-10°C enhances the enrichment factor to 100 and the yield obtained is comparable to that towards the red edge of C-13 absorption (i.e. at 9P(26) laser line). At a given enrichment factor higher enrichment efficiency is achieved when CF 2 HCl is irradiated at lower temperature.