Determination of the electron affinity of astatine

by David Leimbach (Johannes Gutenberg Universitaet Mainz (DE))

Wednesday 10 Jul 2019, 14:15 → 14:45 Europe/Zurich

Astatine, element 85, is the rarest naturally occurring element in earth’s crust. It only exhibits a number of short lived alpha emitting isotopes produced as a daughter from various decay chains. One of the longer lived isotopes, 211At, is of special interest as an agent for targeted alpha therapy (TAT), a method of treating cancer directly at the location of a tumor with alpha emitting particles. Due to its short life-time and scarcity, some fundamental properties of astatine such as the electron affinity (EA), are not yet known. The electron affinity combined with the previously measured ionization potential (IP) determines the electronegativity which serve as valuable benchmark for quantum chemical calculations predicting the chemical properties of this element and its compounds.

The Gothenburg Anion Detector for Affinity measurements by Laser PHotodetachment (GANDALPH) was designed for the determination of the EA of radioisotopes produced at ISOLDE. Following the first measurement of the EA of radiogenic 128I in 2016, GANDALPH has recently received multiple upgrades to facilitate beam tuning and detection of low intensity (<1pA) ion beams. During an experimental campaign at CERN-ISOLDE in 2018, the GANDALPH setup was used to successfully measure the EA of astatine. Experiment and results of these measurements will be presented and compared to expectations and recent theoretical calculations.