Infrared spectroscopy and structures of Ar-n-HF in liquid helium nanodroplets

Infrared spectra are reported for Ar-n-HF complexes up to the closing of th e first solvent shell. These complexes were grown in superfluid helium drop lets, leading to the formation of multiple isomers for n>3. The vibrational frequency shifts associated with the HF stretch are in excellent agreement with previous theoretical calculations. The relative abundances of the var ious isomers is found to be dependent upon the order of pick-up of the HF a nd argon. When HF is added to the droplets first the isomers corresponding to the solvated HF are produced in high abundance. Growth of the argon clus ter prior to addition of the HF leads to the latter being on the "surface" of the argon cluster. (C) 2001 American Institute of Physics.