Resonant two-photon ionization spectroscopy of jet-cooled PdSi.

The spectra of diatomic PdSi have been investigated for the first time, using the technique of resonant two-photon ionization spectroscopy. A number of vibronic transitions have been observed in the 20,400-22,000 cm(-1) range. It is difficult to group the bands into band systems, although one likely band system has been identified. Three bands have been rotationally resolved and analyzed, two of which are perturbed by interactions with other states. The data show that the ground state of PdSi has Ω = 0, and a bond length of r(0)('') = 2.0824(3) Å. Comparisons to previously published density functional theory calculations provide strong support for the assignment of the ground state to the 1σ(2) 2σ(2) 1π(4) 1δ(4) 3σ(2), (1)Σ(+) term, which is predicted to be the ground state in the calculations. The much shorter bond length and greater bond energy of PdSi, as compared to its isoelectronic counterpart, AlAg, demonstrate that there is strong π bonding in PdSi, as has been previously found for the other nickel group silicides, NiSi and PtSi.