The a 3Σ +1(u) ← X 1Σ +(g) band systems of CuAu and Au 2

Abstract

The a 3Σ + 1(u) ← X 1Σ + (g) band systems of jet-cooled CuAu and Au 2 have been spectroscopically observed by resonant two-photon ionization spectroscopy. The upper state vibrational constants (ω′ e = 109.3 cm −1, ω′ e X′ e = 0.90 cm −1 for 63Cu 197 Au; ω′ e = 82.9 cm −1, ω′ e X′ e = 1.01 cm −1 for 197Au 2) indicate shallow excited potential curves, and the long excited state lifetimes (≈ 40 μs for Au 2, ⩾ 90 μs for CuAu) imply a spin-forbidden decay process, in agreement with the assignment of the transition. Birge-Sponer extrapolations give ground state bond strengths of 2.41 ± 0.07 and 2.290 ± 0.015 eV for CuAu and Au 2, respectively. A rotationally resolved scan of 63Cu 97 Au has established the bond lengths as r 0(X 1Σ +) = 2.3303 ± 0.0009 and r 0(a 3Σ + 1) = 2.445 ± 0.026 Å.