The Enhancement of Metallic Silver Monomer Evaporation by the Adhesion of Polar Molecules to Silver Nanocluster Ions
Abstract
We have compared the metallic evaporation channels from metastable Ag(X=5,7,11)(AgI)(Y=1-4)(+) clusters in the 1st FFR of a double focussing mass spectrometer with that of the corresponding pure metallic clusters, Ag(X=5,7,11) (+). It is found that the presence of the polar AgI molecules increases the rate of silver monomer evaporation relative to that of silver dimer evaporation. Using thermodynamic expressions for the heat of evaporation of the different evaporation processes and assuming the absence of reverse activation energies, an expression for the difference between the activation energy of silver monomer and dimer evaporation is derived. It is shown that dipole/induced-dipole forces resulting from the presence of AgI polar molecules lead to an enhancement of silver monomer evaporation if the polarizability of the pure metallic cluster ions increases with the number of Jellium electrons. Our theoretical calculations of the static polarizabilities of (Ag(x))(+) using time dependent density functional theory within the local density approximation, shows a smooth increase in the polarizabilities with the number of the Jellium electrons in these clusters. Finally, we observe that the enhancement of Ag monomer evaporation per AgI added is smaller for clusters with even number of AgI molecules than with odd numbers. This was proposed to result from the contribution of configurations with dipole 'pairing' of the AgI molecules in clusters with even number of AgI molecules. Dipole pairing would decrease the average dipole/induced-dipole interaction between the AgI molecules and the metallic part of these 'mixed' clusters.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 21, 1994
- Accession Number
- ADA284936
Entities
People
- Clifton Fagerquist
- Dilip K. Sensharma
- Marvin L. Cohen
- Mostafa El-Sayed
- Ángel Rubio Secades
Organizations
- University of California, Los Angeles