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??-, deriving from a ??rr? molecular configuration, and is characterized by ?" = 215 cm-1, ?"exe" = 3 cm-1, and r0' = 2.53 ? 0.02 ?. The upper state of the observed band system is 3IIr correlating to the Ga 4s?4p, ?P? + As 4s?4p?, ?D0 excited separated atom limit. A strong predissociation sets in above v'=0 for the ?'=2,1 and 0- components of the 3IIr excited state, and it is proposed that this is induced by spin-orbit interaction with the ??*rr?,??- state which correlates to ground state atomic fragments. Constants for the upper ?IIo+ state are ?'e = 152.13 ? 0.70 cm-1, ?'ex'e = 2.89 ? 0.08 cm-1, and r"e = 2.662 ? 0.027 A for the 69Ga7 5As 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 D0(GaAs) = 2.06 ? 0.05 eV. Comparisons to group IV and other group HI-V diatomics, and to the bulk solid materials are also presented.