SPECTROSCOPY AND ELECTRONIC-STRUCTURE OF JET-COOLED GAAS

An optical spectrum, obtained by resonant two-photon ionization spectroscopy, is reported for jet-cooled diatomic gallium arsenide. The ground state is identified as X 3Σ-, deriving from a σ2π2 molecular configuration, and is characterized by ωe″ = 215 cm-1, ωe″xe″ = 3 cm-1, and r0″ = 2.53 ± 0.02 Å. The upper state of the observed band system is 3Π, correlating to the Ga 4s 24p, 2P0 + As 4s24p3, 2D0 excited separated atom limit. A strong predissociation sets in above v′ = 0 for the Ω′ = 2,1 and 0- components of the 3Π, excited state, and it is proposed that this is induced by spin-orbit interaction with the σσ*π2, 5Σ- state which correlates to ground state atomic fragments. Constants for the upper 3Π 0+ state are ωe′ = 152.13 ± 0.70 cm-1, ωe′xe′ = 2.89 ± 0.08 cm-1, and r′e = 2.662 ± 0.027 Å for the 69Ga75As isotopic modification. The ionization potential of GaAs has been bracketed as IP(GaAs) = 7.17 ± 0.75 eV, and a reevaluation of the third-law measurement of the bond strength provides D 0(GaAs) = 2.06 ± 0.05 eV. Comparisons to group IV and other group III-V diatomics, and to the bulk solid materials are also presented. © 1990 American Institute of Physics.