Characterization of theX 2 ? u + state of7Li 2 ? via negative ion photoelectron spectroscopy

Abstract

The negative ion photoelectron spectrum of7Li 2 − is reported at 488 nm (2.540 eV). Three electronic bands are observed in this spectrum and are assigned to the following photodetachment transitions:7Li2,X 1 ∑ + +e − ←7Li 2 − ,X 2 ∑ + ;7Li2,a 3 ∑ + +e − ←7Li 2 − ,X 2 ∑ + ; and7Li2,A 1 ∑ + +e − ←7Li 2 − ,X 2 ∑ + . The electron affinity of7Li2 is determined to be 0.437±0.009 eV, leading to an anion dissociation energy,D 0, of 0.865±0.022 eV for the ground state of7Li 2 − . A Franck-Condon analysis of the7Li2,X 1 ∑ + +e − ←7Li 2 − ,X 2 ∑ + band yields the following spectroscopic constants for the ground state of7Li 2 − :B e =0.502±0.005 cm−1,r e =3.094±0.015 A, and ω e =232±35 cm−1.