Enhanced positron annihilation on polyatomic molecules is a long-standing and complex problem. We report the results of calculations of resonant positron annihilation on methyl halides. A free parameter of our theory is the positron binding energy. A comparison with energy-resolved annihilation rates measured for ${\mathrm{CH}}_3\mathrm{F}$, ${\mathrm{CH}}_3\mathrm{Cl}$, and ${\mathrm{CH}}_3\mathrm{Br}$ [L. D. Barnes et al., Phys. Rev. A 74, 012706 (2006)] shows good agreement and yields estimates of the binding energies.

• Received 29 August 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.193201