PHOTODISSOCIATION STUDY ON MG-5 - ELECTRONIC-STRUCTURE AND PHOTOINDUCED INTRACLUSTER REACTION((H2O)(N), N=1)

Photodissociation spectra of Mg+(H2O)(n) (n=1-5) cluster ions: were ex amined in the wavelength region from 720 to 250 nm by monitoring the t otal yield of the fragment ions. The absorption bands exhibit redshift s as large as 17000 cm(-1) with respect to the P-2-S-2 resonance line of the free Mg+ ion and were explained by the shift of this transition as a result of hydration. The spectra also exhibit clear evolution of solvation shell with;the first shell closing at n=3, being consistent with the theoretical prediction. The mass spectra of the fragment ion s show the existence of two dissociation processes: the evaporation of water molecules and the photoinduced intracluster reaction to produce the hydrated MgOH+ ion, MgOH+(H2O)(m). The branching fraction between the two processes depends strongly on the solvent number n and also o n the photolysis wavelength. The energetics and the dynamics of the di ssociation processes were discussed in conjunction with the results of ab initio calculations.