Laser isotope separation and the multiphoton decomposition of methanol using a pulsed HF or DF laser

The focussed beam from a single line P₁(6)] pulsed HF laser has been used to decompose CH₃OH (for pressures between 0.169 and 14.95 kPa) and isotopic mixtures of methanol. The normalized yields (number of product molecules Pulse/P_METHANOL) of the non-condensable products H₂, CO and CH₄ increased linearly with pressure (for the range ≈ 1 - 7 kPa). For sufficiently low pressures, selective excitation of one component of an isotopic mixture gives an isotopically enriched product. For example, selective excitation of CH₃OH in equimolar of mixture CH₃OH/CH₃OD at a total pressure of 269 Pa gives hydrogen which is enriched 60-fold in H versus D. The degree of isotopic enrichment decreases with increasing mixture pressure. The efficiency of conversion of photon energy to reaction product has been observed to increase linearly with pressure. Decomposition studies have been performed in the presence of additives. These imply that the decomposition of methanol to H₂ involves mainly molecular rather than free radical steps.