THE LASER-DROP METHOD - A NEW APPROACH TO INDUCE MULTIPLE-PHOTON CHEMISTRY WITH PULSED LASERS - EXAMPLES INVOLVING REACTIONS OF DIPHENYLMETHYL AND CUMYLOXYL RADICALS

A new method, described as the laser-drop technique, is presented which allows preparative experiments in laser-induced multiphoton chemistry. The technique shares most of the advantages of the successful laser-jet technique but allows the use of pulsed lasers that are readily available in many laboratories. The laser-drop method has been tested with two photochemical systems. The well-studied diphenylmethyl radical system allows a direct comparison of results from laser-drop, laser-jet, lamp, and two-color two-laser studies. The laser-jet and laser-drop techniques show comparable performance for two-photon processes, but the latter has advantages in reactions of higher order in light intensity. The photolysis of dicumyl peroxide has been used to demonstrate for the first time laser-induced beta-cleavage of alkoxyl radicals. Photolysis of dicumyl peroxide in methanol leads to dramatically different product distributions under conditions of lamp and laser-drop photolysis.