S.Katayama, R.Nishio, H.Kuroda, K.Awazu
Univ. of Shizuoka, IR FEL Research Center,Chiba, FEL Research Institute,Osaka
Strong infrared FEL irradiation, average power (Pex) 5mW,led ethylacetate in an alkali solution to a photodynamical process. It was a hydrolysis reaction to ethanol and aceticacid, whose products were clearly identified by gaschromatography and NMR. Although the products are the same as those produced by the thermic hydrolysis, the reaction mechanism must be essentially different from that of the hydrolysis. The mechanism can be explained by such a process that the ethylacetate molecule absorbs multi-photons (wave length 5.75 micrometer), which corresponds to the C=O stretching vibration. According to references, an activation energy of the hydrolysis under basic condition is 11 kcal/mol, which is extremely small compared with that of the other hydrolysis. This suggests that the FEL exposure may easily exceed the activation energy. In practice, however, during the FEL irradiation, no temperature rise of the sample was observed.This means that although the FEL irradiation causes a local temperature rise in the molecule, most of the absorbed energy get immediately scattered in the other energy forms and lost because of relaxation effect. Irrespective of such the relaxation, transient flux can often exceed the potential barrier of the activation energy and then the photodynamical reaction occurs.
