Infrared spectra of the Cl--C2H4 and Br--C2H4 anion dimers

Abstract

Infrared spectra of mass-selected Cl--C2H4 and Br--C2H4 complexes are recorded in the vicinity of the ethylene CH stretching vibrations (2700 3300 cm-1) using vibrational predissociation spectroscopy. Spectra of both complexes exhibit 6 prominent peaks in the CH stretch region. Comparison with calculated frequencies reveal that the 4 higher frequency bands are associated with CH stretching modes of the C2H4 subunit, while the 2 weaker bands are assigned as overtone or combinations bands gaining intensity through interaction with the CH stretches. Ab initio calculations at the MP2/aug-cc-pVDZ level suggest that C2H4 preferentially forms a single linear H-bond with Cl- and Br- although a plana..