Abstract

The passage of nuclear fission fragments through thin solid films produces a fission track. Measurement of the kinetic energy and angular distribution of ion emitted from the track give evidence for the formation of a superradiant state containing a high density of molecules simultaneously excited by the intense electromagnetic field associated with the fission fragment. The radiation emitted in two narrow cones at 0/sup 0/ and 180/sup 0/ to the fission fragment direction develops strong hypersonic pulses by stimulated Brillouin scattering. These nonlinear processes have two effects: molecules in the fission track are electronically and vibronically excited and can undergo fast chemical reactions in the excited state, and reaction products formed on the surface have a high probability of being emitted when the hypersonic pulse reaches the surface. If the reaction products are charged, they can be characterized by mass spectrometry. Electron transfer reactions have been studied with chlorophyll-a as a model compound. Molecular aggregates of chlorophyll produce a singlet exciton state characterized by an electron exchange current within the the aggregate. This was verified directly by observing the breakup of this state into (CHl-a)/sup +/ and (Chl-a)-ions. Molecules that form aggregates in the solid state, mediated by hydrogen bondingmore » where the H/sup +/ is weakly bound (acidic), give evidence of proton charge transfer in the singlet exciton states. Amino acids, peptides, and small oligonucleotides exhibit this reaction. Molecules forming aggregates that do not produce a charge delocalization do not form separated ion pairs in the excited state. The reactions that do occur involve charge exchange (-OH + Na/sup +/ ..-->.. -ONa + H/sup +/) and cation attachment (M + Li/sup +/ ..-->.. MLi/sup +/). Alpha cyclodextrin has been a good model molecule for these studies.« less

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