Pd-Ga model SCALMS: Characterization and stability of Pd single atom sites

•Model Pd-Ga SCALMS were studied by IRAS in combination with DFT calculations.•Pd-Ga with Pd:Ga ratio <0.1 form at 300 K an alloy exposing isolated Pd sites only.•CO on such sites has a binding energy of 1.1 ± 0.2 eV and frequency of 2081 cm−1.•Pd-Ga particles on HOPG are stable below the melting temperature of the Pd-Ga alloy.•Calculations corroborate the Pd isolation and show CO frequencies of 2058–2067 cm−1.