Infrared vibronic absorption spectrum and spin–orbit calculations of the upper spin–orbit component of the Au3 ground state

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Abstract
Laser-ablated gold co-deposited with excess neon at 3.5 K produces a new sharp 2025.5-cm−1absorption.Annealing to 8 K increases this absorption ten-fold and produces six weaker associated vibronic bands with 172- and 118-cm−1 intervals. Relativistic configurations (RCI) computations are carried out for several electronic states lying below 4.4 eV. These calculations show that the spin–orbit effect stabilizes the D 3h structure and quenches Jahn–Teller distortion. They also predict a 0.2-eV spin–orbit splitting of the Au 3 ground state, which is in excellent agreement with the 2025.5-cm−1 neon matrix band origin. We have also confirmed the assignment of the A-X system at 1.8 eV observed by Bishea and Morse. The observed vibronic intervals are in accord with calculated a 1 ′ and e ′ stretching fundamentals and they confirm the D 3h geometry for Au 3 . This work reports the first observation of the ground-state spin–orbit splitting of a heavy metal trimer.