CHARACTERIZATION OF THE X(2)SIGMA(U)(-7(2-) VIA NEGATIVE-ION PHOTOELECTRON-SPECTROSCOPY() STATE OF LI)

The negative ion photoelectron spectrum of (Li2-)-Li-7 is reported at 488 nm (2.540 eV). Three electronic bands are observed in this spectru m and are assigned to the following photodetachment transitions (Li2)- Li-7, X1 SIGMA(g)+ + e- <-- (Li2-)-Li-7, Li2-(Li-7) a3 SIGMA(u)+ e- <- - (Li2-)-Li-7, X2 SIGMA(u)+; and (Li2)-Li-7, A1 SIGMA(u)+ + e- <-- (Li 2-)Li-7, X2 SIGMA(u)+. The electron affinity of (Li2)-Li-7 is determin ed to be 0.437 +/- 0.009 eV, leading to an anion dissociation energy, D0, of 0.865 +/- 0.022 eV for the ground state of (Li2)-Li-7. A Franck -Condon analysis of the (Li2)-Li-7 X1 SIGMA(g)+ + e- <-- (Li2-)-Li-7, X2 SIGMA(u)+ band yields the following spectroscopic constants for the ground state of (Li2-)-Li-7: B(e) = 0.502 +/- 0.005 cm-1, r(e)=3.094 +/- 0.015 angstrom, and omega(e) = 232 +/- 35 cm-1.