Positron binding to alcohol molecules

Abstract

Abstract. Results are presented for positron binding to a selection of molecules containing the hydroxyl functional group. These molecules, which span in the range of carbon atoms from 1 (methanol) to 4 (1-butanol), have moderate permanent dipole moments ranging from about 1.4 to 2.4 D. The dependence of the binding energy on the magnitude of the molecular dipole polarizability and static dipole moment is studied. An effect that appears to be due to the localization of the bound positron is discussed. Contents

Theoretical investigation of a positron binding to an aspartame molecule using the ab initio multicomponent molecular orbital approach

“…Analyzing the positron binding to aspartame molecule at given nine equilibrium conformers, we theoretically confirmed the strong correlation between the PA and dipole moment. As reported in the recent experimental works by Surko and coworkers, conversely, the PA values were measured via the vibrational Feshbach resonance (VFR) in which a vibrational mode absorbs the excess energy, and thus the molecular vibrational excited states can be resonant with the temporary bound state of a positron and molecule. The mechanism of positron binding via VFR measurements could be different to a positron attachment in a given molecular equilibrium structure as demonstrated in our calculations .…”

“…Positrons injected into a liquid or solid induce processes such as ionization, electronic excitation, the formation of positronium (a meta‐stable bound state of a positron and an electron), and the formation of positronic molecular complexes, before the positron undergoes pair‐annihilation with an electron. Recently, Surko and coworkers experimentally analyzed positron annihilation on some molecular species. They have measured positron binding energies [positron affinity (PA)] for many molecular species and have discussed the relationship between the positron binding and the properties of the parent molecule.…”

Positronium formation in methanol and ethanol

“…Those which do not are considered to have formed Ps or to have been annihilated. As discussed by Jones et al [8], enhanced annihilation can occur with molecules like methanol and ethanol below ∼1 eV incident energy, but the resultant annihilation cross section is still orders of magnitude lower than the scattering cross sections of interest here, and thus direct annihilation as a loss mechanism is neglected. Another problem with these alcohols is the enormous increase in Q tot below a few eV, attributed by Zecca et al [1] to the polarizability of the molecules.…”

Formation of positron-atom bound states in collisions between Rydberg Ps and neutral atoms

“…The downshift of a resonance relative to the vibrational excitation energy provided a measure of * aswann02@qub.ac.uk † d.cassidy@ucl.ac.uk ‡ a.deller@ucl.ac.uk § g.gribakin@qub.ac.uk the positron binding energy. This has enabled positron binding energies to be determined for over seventy molecules [19][20][21][22].…”