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

Abstract

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.