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.