The electron affinity of thulium has been measured using laser photodetachment electron spectroscopy. The electron affinity of $\mathrm{Tm}{(}^2{F}_{7/2})$ was determined to be $1.029\pm 0.022\mathrm{eV}.$ The data also show that ${\mathrm{Tm}}^{\mathrm{-}}$ has at least one bound excited state with a binding energy of $0.979\pm 0.017\mathrm{eV}$ relative to the ground state of the thulium atom. The present experimental measurements are compared to a recent calculation of the electronic structure of ${\mathrm{Tm}}^{\mathrm{-}}$ and a recent experimental investigation of ${\mathrm{Tm}}^{\mathrm{-}}.$

• Received 5 September 2001

DOI:https://doi.org/10.1103/PhysRevA.65.010501