The Infrared Multiphoton Photochemistry of Methanol

Stephen E. Bialkowski, Utah State University
William A. Guillory


CO2 TEA laser has been used to initiate the multiphoton dissociation of CH3OH, both pure and with NO added as a free radical scavenger. The decomposition of CH3OH at the high power density of the focused laser radiation results in molecular and free radical initiated products. Decomposition through molecular intermediates appears to proceed via CH3OH+nhν→CH2O∗+H2 and CH2O∗ →CO+H2, and comprises ∼90% of the consumed CH3OH in ∼3000 laser pulses. The radical initiated process CH3OH+nhν→CH3 +OH ultimately results in the stable products C2H4, C2H2, and CH4 to an extent of ∼10% of the CH3OH consumed. Luminescence from the focal zone is due to emission from OH†, CH†, C†2, and possibly CH2O†. Stable products as well as the visible luminescence due to the electronically excited diatomic radicals are followed as a function of pressure, time, and addition of the free radical scavenger gas NO. Both major photodecomposition routes appear to be non‐Boltzmann.