The heat absorbed when chlorodifluoromethane (CF2HCI) and ethyl acetate were irradiated with a pulsed infrared CO+-TEA laser was mcxured using a laser calorimeter_ The measurements show that CF2HCl at hi* pressure ( > 10 torr) was completely thermally equilibrated during the Iaser puke, while at low pressure (< 2 to@ this system deviated considerably from thermal equilibrium-EthyI acetate, however, was found to be non-thermal over the entire pressure range studied (05 to 20 torr). Implications of these obrer.arions to infrared induced unimolecular decompositions and molecular energy 'Janrer are discuned.
I_ introduction
Any quantitative description of multiphoton induced decomposition of polyatomic molecules must ultimately be based on information regarding the degree of dissociation as a function of the energy absorb-ed_ This paper deals with the detemtiation of the Iatter quantity and its application to stludies on the decomposition of CF2HCI and ethyl acetate. Grunwald and co-workers [l] have approached this problem through the measurement of power loss. Their measurements were performed on optically thick systems_ OpticaI thickness results in thermal gradients in the laser cell and leads to results which are at best ambiguous. However, working with optically thin systems results in the complication that a power loss measurement of necessit--involves taking the difference between two large numbers which then re&ts in impaired precision-YabIonovitch and co-workers 123 have used optical acoustic detection_ This is not a difference measurement, but the device must be calibrated absolutely and there may be certain experimental dif-