SPECTROSCOPY OF WEAKLY-BOUND MAGNESIUM-ION COMPLEXES

Weakly bound complexes of the form Mg+ -L (L = CO2, H2O, N2, Ar, etc.) are prepared in a pulsed nozzle/laser vapourization cluster source an d studied in the molecular beam environment. The ion complexes are jet cooled and mass selected in a specially designed reflectron time-of-f light mass spectrometer for their study. The mass-selected ions are ex cited with a tunable dye laser, and the products, if any, from photodi ssociation are mass analysed and detected as a function of the excitat ion laser wavelength. This photodissociation spectroscopy experiment r eveals the decomposition channels of excited complexes and their absor ption spectra. Photodissociation channels vary from simple metal ion-l igand bond breaking, to metal-to-ligand charge transfer, to metal inse rtion/elimination reactions in the excited state. In reactive systems, the spectra are broad and featureless. However, in systems with simpl e metal-ligand dissociation, vibrational and partial rotational resolu tion is obtained in the spectra. The detailed analysis of this structu re makes it possible to determine the structures of metal ion complexe s and their metal-ligand binding energies.