Model for the charge-transfer probability in helium nanodroplets following electron-impact ionization

Andrew M. Ellis, Shengfu Yang
2007 Physical Review A. Atomic, Molecular, and Optical Physics  
A theoretical model has been developed to describe the probability of charge transfer from helium cations to dopant molecules inside helium nanodroplets following electron impact ionization. The location of the initial charge site inside helium nanodroplets subject to electron impact has been investigated and is found to play an important role in understanding the ionization of dopants inside helium droplets. The model is consistent with a charge migration process in small helium droplets that
more » ... s strongly directed by intermolecular forces originating from the dopant, whereas for large droplets (tens of thousands of helium atoms and larger) the charge migration increasingly takes on the character of a random walk. This suggests a clear droplet size limit for the use of electron impact mass spectrometry for detecting molecules in helium droplets. + 2 He [4] Recent work by Lewis et al. has added substantially to the understanding of charge transfer processes in helium nanodroplets. In one study, the threshold photoelectron-photoion coincidence (TPEPICO) technique was employed to investigate the fragmentation mechanism and energetics of helium droplets doped with triphenylmethanol after electron impact ionization [7]. In another recent study, Lewis and co-workers developed the technique of optically-selected mass
doi:10.1103/physreva.76.032714 fatcat:gv5wunrdsfbn5dpfmubp2nn6vm