Infrared Spectra of Size Selected Cl-−(D2) n and F-−(D2) n Anion Clusters

Infrared vibrational predissociation spectra are reported for size-selected F-−(D2) n (n = 1−6) and Cl-−(D2) n (n = 1−3) clusters in the D−D stretch region. The F-−(D2) n and Cl-−(D2) n spectra each feature a single band shifted to lower energy from the bare D2 stretching frequency that moves to higher frequency with increasing cluster size. Vibrational band shifts are substantially larger for F-−(D2) n than for Cl-−(D2) n , reflecting the stronger F-- - -D2 interaction. The spectra are compatible with the F-−(D2) n and Cl-−(D2) n clusters containing roughly equivalent D2 ligands that are attached end-on to a central halide anion core. The unobserved D−D stretch band of the F-−D2 complex is predicted to lie at ∼2400 cm-1.