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 and studied in the molecular beam environment. The ion complexes are jet cooled and mass selected in a specially designed reflectron time-of-flight mass spectrometer for their study. The mass-selected ions are excited with a tunable dye laser, and the products, if any, from photodissociation are mass analysed and detected as a function of the excitation laser wavelength. This photodissociation spectroscopy experiment reveals the decomposition channels of excited complexes and their absorption spectra. Photodissociation channels vary from simple metal ion-ligand bond breaking, to metal-to-ligand charge transfer, to metal insertion/elimination reactions in the excited state. In reactive systems, the spectra are broad and featureless. However, in systems with simple metal-ligand dissociation, vibrational and partial rotational resolution is obtained in the spectra. The detailed analysis of this structure makes it possible to determine the structures of metal ion complexes and their metal-ligand binding energies.