Photodissociation laser isotope effects

Marked differences in the laser action (1.315 μm) observed following the flash photolysis of CD₃I and CH₃I are reported (substantially greater outputs are observed with CD₃I). These differences result from the significantly smaller cross section for quenching of I(5 ²P ) by CD₃I, relative to that for CH₃I. Absolute values for the quenching cross sections have been determined using time resolved atomic absorption spectrophotometry. These data were employed in a computer simulated model which satisfactorily reproduced the light output from CH₃I, CD₃I and CF₃I photochemical laser systems. It is concluded that isotopic substitution can markedly influence the cross section for quenching of an excited state and thus influence partitioning between the various available channels.