Attila Kovács and Rudy J. M. Konings

Trimer Formation of AgI.

A Gas-Phase FT-IR and Theoretical Study.

Journal of Molecular Structure, 643 (2002) 155-160


The vapour above AgI has been investigated in the range of 375-70 cm-1 by FT-IR spectroscopy.  The spectrum shows two close-lying bands attributed to the stretching modes of silver iodide monomer (AgI) and trimer (Ag3I3).  The bands have been assigned on the basis of thermodynamic and quantum chemical calculations.  The thermodynamic analysis of the vapour composition revealed the major contribution of Ag3I3(g) up to 900 K while its abundance decreases at higher temperatures.  This trend is in agreement with the observed relative band intensities in the IR spectrum.  A comparative theoretical study of the analogous Ag3Br3 and Ag3Cl3 trimers justified the interchanging relative order of the stretching frequencies of AgX and Ag3X3 when going from X = Cl to I.