Measurements are presented for the low-energy positron annihilation spectra of the alkane molecules propane through octane. The downshift of the vibrational Feshbach resonances of the infrared-active C-H stretch vibrational modes is used to obtain updated values for the positron-molecule binding energies for these molecules. These binding energies correct previously reported values which had systematic energy shifts due to several small, but significant, errors in the analyses. Once these energy shifts are corrected, the old and new measured spectra are in good agreement. This updated analysis procedure is applied to other previously measured alkanes, providing updated binding energies for these molecules. The resulting data are shown to be in good agreement with a recent model-potential calculation and solve issues regarding the interpretation of previous measurements.

• Received 24 March 2023
• Accepted 10 July 2023

DOI:https://doi.org/10.1103/PhysRevA.108.032801