Excitation functions threshold behavior

For the three-atom reactions, none of the exoergic processes is adequately described by the theory. A possible exception is reaction (iv), for which no quantitative treatment has been published this is needed. For the endoergic processes, encouraging agreement is indicated for reaction (xv), but the detailed information available from the phase-space calculation needs to be compared with Chupka s experimental data. Experimental data are needed for reactions (v), (xvi), and (xvii). Finally, the overall shapes of the excitation functions agree well for (xi) and (xiii), but there would appear to be a significantly different behavior for (vi) at and above the reaction threshold. The two studies of four-atom reactions offer encouragement, but substantial uncertainties remain as to the validity of these comparisons. 

OL behavior is assessed simply by monitoring the transmission of a (usually solution) sample as a function of the incoming laser fluence measured in joules per square centimeter (rather than intensity in watts per square centimeter).22,23 Limiting thresholds Fth, defined as the incident fluence at which the actual transmittance falls to 50% of the corresponding linear transmittance, are then commonly quoted. Since excited-state absorption processes generally determine the OL properties of molecules, the excited-state structure and dynamics are often studied in detail. The laser pulse width is an important consideration in the study of OL effects. Compounds (1-5)58-62 are representative non-metal-containing compounds with especially large NLO and/or OL... 

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