Electric Deflection of Middle-Size Ammonia Clusters Containing (e-Na+) Pairs

ÁLVARO CARRERA; ERNESTO MARCECA

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Lugar: Washington; Año: 2015 vol. 119 p. 4207 - 4213

1089-5639

Effective polarizabilities of Na(NH3)n (n = 8-27) clusters were measured by electric deflection as a function of the particle size. A significant field-induced shift of the beam intensity profile without the occurrence of broadening revealed that the clusters behave as ?liquid-like? polar objects in the conditions of the experiment (cluster temperatures were estimated in the range of 110-145 K). Most of the cluster polarity is attributed to the spontaneous promotion of the alkali atom valence electron to a diffuse state stabilized by the cluster solvent field, with the consequent formation of (e-, Na+) pairs. The average modulus of the dipole of Na-NH3 clusters, mu0, was determined using the Langevin-Debye theory, and the data was compared with previous measurements obtained for Na-H2O clusters. Sodium-doped ammonia clusters exhibit much larger mu0 values and a step size dependence which is not present when the solvent is water. This evidence suggests that while the (e-, Na+) structure is rather compact in Na(H2O)n clusters and remains almost unchanged during the solvation process, in Na(NH3)n the unpaired electron abandons the proximity of the Na+ ion and gradually extends and occupies new solvent shells.