Measurement of the electron affinity of thulium

The electron affinity of thulium has been measured using laser photodetachment electron spectroscopy. The electron affinity of Tm(2F7/2) was determined to be 1.029±0.022eV. The data also show that Tm- has at least one bound excited state with a binding energy of 0.979±0.017eV relative to the ground state of the thulium atom. The present experimental measurements are compared to a recent calculation of the electronic structure of Tm- and a recent experimental investigation of Tm-.