Infrared spectra of size selected Cl-(D) and F-(D) anion clusters

Infrared vibrational predissociation spectra are reported for size-selected F--(D-2)(n) (n = 1-6) and Cl--(D-2)(n) (n = 1-3) clusters in the D-D stretch region. The F--(D-2)(n) and Cl--(D-2)(n) spectra each feature a single band shifted to lower energy from the bare D-2 stretching frequency that moves to higher frequency with increasing cluster size. Vibrational band shifts are substantially larger for F--(D-2)(n), than for Cl--(D-2)(n), reflecting the stronger F-- - -D-2 interaction. The spectra are compatible with the F--(D-2)(n) and Cl--(D-2)(n) clusters containing roughly equivalent D-2 ligands that are attached end-on to a central halide anion core. The unobserved D-D stretch band of the F--D-2 complex is predicted to lie at similar to2400 cm(-1).