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 ω″e=215 cm−1, ω″ex″e=3 cm−1, and r″0=2.53±0.02 Å. The upper state of the observed band system is 3Πr correlating to the Ga 4s24p, 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 3Πr 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 3Π0+ state are ω′e=152.13±0.70 cm−1, ωex′e=2.89±0.08 cm−1, and re=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 re-evaluation of the third-law measurement of the bond strength provides D0(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.