Vibrational spectroscopy in the ultraviolet via Gd3+ fluorescence: application to biological systems.

Coupling of the narrow 311-nm Gd3+ fluorescence transition with the vibrational transitions of its inner-sphere ligands gives rise to the emission of vibronic photons between 320 and 350 nm. The energy difference between the fluorescence and vibronic transitions is equal to that of the vibrational transitions of the molecular group coordinated to Gd3+; thus the ir spectrum of the ligand can be measured in the uv spectral region the presence of other molecules absorbing in the ir. The vibronic spectra of several biological, organic, and inorganic molecules are shown to accurately report the vibrational spectrum of the ligand.