Unravelling the electronic structure of the silicon dimer using threshold photoelectron spectroscopy

Ning Chen (1) , Bérenger Gans (1) , Sebastian Hartweg (2) , Gustavo Garcia (1) , Séverine Boyé-Péronne (1) , Jean-Christophe Loison (3)

1 ISMO - Institut des Sciences Moléculaires d'Orsay
2 SSOLEIL - Synchrotron SOLEIL
3 ISM - Institut des Sciences Moléculaires

The low-lying electronic states of silicon dimer (Si2) and its cation (Si + 2) have been studied by single-photon photoelectron spectroscopy combining a flow-tube reactor, vacuum-ultraviolet synchrotron radiation, and a double imaging photoelectron/photoion spectrometer. The energy range covered in this study (7.0 − 9.5 eV) allowed to observe several photoionising transitions involving the three lowest electronic states of Si2 (X 3 Σ − g , D 3 Πu, a 1 ∆g) and five of the six lowest states of Si + 2 (X + 4 Σ − g , a + 2 Πu, b + 2 ∆g, c + 2 Σ − g , and e + 2 Πu). Using ab initio calculations and Franck-Condon simulations, several electronic transitions are identified which bring new elements in the description of the dense electronic landscapes of the silicon dimer and its cation. Interestingly, one of the most intense transitions is spin-forbidden (X + 4 Σ − g ← a 1 ∆g) and is most probably observed through autoionisation processes by spin interactions.

Keywords: threshold photoelectron; silicon dimer; flow-tube reactor; radical production; VUV spectroscopy

Domains: Chemical Physics [physics.chem-ph]

Ning Chen, Bérenger Gans, Sebastian Hartweg, Gustavo Garcia, Séverine Boyé-Péronne, et al.. Unravelling the electronic structure of the silicon dimer using threshold photoelectron spectroscopy. Molecular Physics, In press, ⟨10.1080/00268976.2022.2140721⟩. ⟨hal-04213599⟩