Threshold energies for dissociative electron attachment to HBr.HX clusters with different HX partners: an ab initio study

Potential energy surfaces and threshold energies for dissociative attachment (DA) of an electron to HBr.HX clusters, viz., e-+HBr.HX→H+Br.HX- have been investigated for HX=HBr, HCl, HF and Kr by ab initio calculations at MP2 and CCSD(T) levels with large basis sets. The results show that all three hydrogen halides reduce the threshold energy to zero, while the reduction for the inert gas is much less. These results are in agreement with experimental studies, which show that capture cross sections for thermal energy electrons for the HX=HBr and HCl systems are close to the theoretical maximum. Very substantial reductions in DA threshold can be achieved by clustering, even when only one clustering partner is involved. The extent of reduction appears to depend on the initial starting geometry in the neutral dimer and other factors, as well as the magnitude of the Br−..HX binding energy.