FTIR-spectroscopy of isolated and argon coated (HBr)n≤4 clusters in supersonic slit-jet expansions

Presented are the ragout-jet FTIR spectra of isolated (HBr)(n) clusters (nless than or equal to4) in pulsed slit-jet expansions. These are the first gas phase infrared spectra of (HBr)(3) and (HBr)(4) reported so far. The assignment is based on a direct comparison with hydrogen chloride and MP2/6-311++G(d,p) ab initio calculations. Despite the well known difficulties of standard ab initio methods and standard basis sets to predict frequency shifts in hydrogen halide clusters, the method and basis set chosen in this work gives at least a correct qualitative description. In addition argon coated HBr clusters up to the tetramer could be observed in co-expansions of HBr with argon, confirming the general capability of the ragout-jet spectroscopy to investigate argon coated molecular clusters of a wide variety of molecules.