The ground state and excited d‐hole states of CuAu

Resonant two‐photon ionization spectroscopy has been applied to jet‐cooled diatomic CuAu. Eight band systems have been observed, rotationally resolved, and analyzed. The ground state is X 1Σ+ in symmetry, deriving from the 3d10Cu5d10Auσ2 molecular configuration. Its bond length has been determined as r0=2.3302±0.0006 A (1σ error limits). The first excited state is the a 3Σ+ state, which derives from the 3d10Cu5d10Auσ1σ*1 molecular configuration. This state possesses a nominal bond order of zero, but is nevertheless bound by D0=1157±150 cm−1 and has a bond length of 2.428±0.028 A. It is observed through the a 3Σ+–X 1Σ+ transition which is very weak, with f≊5×10−5. Seven higher energy band systems are also observed, most of which correlate asymptotically to d‐hole states described by the Cu 3d104s1, 2S+Au 5d96s2, 2D5/2, Cu 3d94s2, 2D5/2+Au 5d106s1, 2S, and Cu 3d94s2, 2D3/2+Au 5d106s2, 2S separated atom limits. The D 0+ excited state, however, displays a very large oscillator strength in transitions with the...