Vibrational Feshbach Resonances Mediated by Nondipole Positron-Molecule Interactions
arXiv:1708.04938 · doi:10.1103/PhysRevLett.119.113402
Abstract
Measurements of energy-resolved positron-molecule annihilation show the existence of positron binding and vibrational Feshbach resonances. The existing theory describes this phenomenon successfully for the case of infrared-active vibrational modes which allow dipole coupling between the incident positron and the vibrational motion. Presented here are measurements of positron-molecule annihilation made using a recently developed cryogenic positron beam capable of significantly improved energy resolution. The results provide evidence of resonances associated with infrared-inactive vibrational modes, indicating that positron-molecule bound states may be populated by nondipole interactions. The anticipated ingredients for a theoretical description of such interactions are discussed.
5 pages, 2 figures, Phys. Rev. Lett. (in press)