INFRARED-SPECTRA OF FEH, FEH2, AND FEH3 IN SOLID ARGON

Reactions of laser ablated iron atoms with hydrogen molecules in a condensing argon stream gave the strong 1660.8-cm(-1) absorption of FeH2 and new weaker 1767.0- and 1646.1-cm(-1) bands which are assigned to the FeH and FeH3 molecules. The formation of all three molecules during sample deposition is the main difference with thermal evaporation experiments where photolysis was required to form FeH2. The primary reaction is insertion of energetic iron atoms to form FeH2 which is relaxed and stabilized by the matrix; however, some decomposition to FeH and Il does occur as FeH is also trapped. A weaker FeH2 satellite band is assigned to Fe2H4. Annealing decreases FeH and FeH2 and increases the band assigned to FeH3. A strong kinetic isotopic effect was found in this system, which is in agreement with previous work.