  Measured and calculated positron binding energies are presented for a range
of hydrocarbons with up to six carbon atoms (viz., methane, acetylene,
ethylene, ethane, propane, butane, and hexane) and their chlorinated
counterparts. Both experiment and theory confirm the large effect that the
chlorine atoms have on the positron binding energy and the strong sensitivity
of the binding energy to the exact position of the chlorine atoms. The
experimental binding energies have been obtained by measuring positron resonant
annihilation using a trap-based positron beam. The calculations are performed
using the previously developed model-correlation-potential method [A. R. Swann
and G. F. Gribakin, J. Chem. Phys. 149, 244305 (2018)]. The overall trends are
discussed with regard to the molecular polarizability, dipole moment, and
geometry. Good agreement between theory and experiment is found, with the
exception of the chlorinated ethylenes and chlorinated hexane. Calculations of
the electron-positron annihilation rate in the bound state are also presented.
