Site-selected fluorescence spectra of (n-C4H9)4NUO2(NO3)3 in poly(methyl methacrylate)

The emission spectrum of (n-C4H9)4 NUO2(NO3)3 in poly(methyl methacrylate) at ca. 8 K has been measured using three laser lines for excitation. The three emission spectra differ in the energy of the origins and hence in the energy of associated progressions, but not in energy separations. These differences correlate with the energy shift of the exciting laser line from the maximum of the solvent-broadened absorption band. This shows that the site-selection process is operative and that site integrity is maintained over quite large excitation-emission energy differences. The intensity distribution in the emission spectrum also depends on this energy shift, and indicates that sites corresponding to the absorption band maximum interact least with the polymer matrix. Similar results for UO2(NO3)2.6H2O are presented. (author)