Deposition of molecular probes in heavy ion tracks

By using polarized fluorescence techniques the physical properties of heavy ion tracks such as the dielectric number, molecular alignment and track ra dius can be traced by molecular fluorescence probes. Foils of poly(ethylene terephthalate) (PET) were used as a matrix for the ion tracks wherein fluo rescence probes such as aminostyryl-derivatives can be incorporated using a suitable solvent, e.g. N,N'-dimethylformamide (DMF) as transport medium. T he high sensitivity of fluorescence methods allowed the comparison of the p robe properties in ion tracks with the virgin material. From the fluorescen ce Stokes shift the dielectric constants could be calculated, describing th e dielectric surroundings of the molecular probes. The lower dielectric con stant in the tracks gives clear evidence that there is no higher accomodati on of the highly polar solvent DMF in the tracks compared with the virgin m aterial. Otherwise the dielectric constant in the tracks should be higher t han in the virgin material. The orientation of the molecular probes was exa mined by polarized fluorescence spectroscopy. It is shown that deposited mo lecular probes with a high aspect ratio have a preferential orientation par allel to the ion track axis.