Study of the low-lying electronic states of Si2 and Si−2 using negative ion photodetachment techniques

Abstract

The low-lying electronic states of Si−2 and Si2 were studied using both photoelectron spectroscopy and threshold photodetachment spectroscopy of Si−2 . Our measurements show that the ground state of Si2 is the X 3Σ−g state and that the X 3Σ−g–D 3Πu splitting is 0.083±0.010 eV. Additional spectroscopic constants for the X 3Σ−g, D 3Πu, a 1Δg, b 1Πu and c 1Σ+g states of Si2 were also determined. For Si−2 , the first two electronic states were identified as: 2Πu (Te =0, re =2.207±0.005 Å, and ν=533±5 cm−1) and 2Σ+g (Te =0.025±0.010 eV, re =2.116±0.005 Å, and ν=528±10 cm−1). The electron affinity for Si2 was found to be 2.176±0.002 eV. Our results provide definitive orderings and splittings for the low-lying electronic states in both Si2 and Si−2 .