Photochemical enrichment of the chlorine and carbon isotopes induced in Freon (CF2Cl2) by CO2 laser pulses

Enrichment of the carbon isotopes by photodissociation or photochemical reaction of Freon (CF2Cl2) induced by a TEA-CO2 laser has been reported recently by several authors. The present work shows that large effects on the chlorine isotopes are also induced. Their laser-wavelength dependence has been measured, and some complementary information on the carbon isotopic effects has been collected. Excitation around 930 cm−1 yields an enrichment in 37Cl in the residual CF2Cl2, and excitation around 1085 cm−1 has an opposite effect, while 13C enrichment is found around both 1090 and 922 cm−1 and 12C enrichment is found around 1065 cm−1. These effects can be qualitatively explained with the known fundamental vibrations ν1 (922 cm−1, stretching mode) and ν6 (992 cm−1, rocking mode) of CF2Cl2. The efficiency of the photodissociations of CF2Cl2 induced by a CO2 laser is evaluated, and an effective threshold energy density of 3 J/cm2 is found at 1089 cm−1.