Threshold photodetachment zero-electron kinetic energy spectroscopy of Si−3

Abstract

The threshold photodetachment zero-electron kinetic energy (ZEKE) spectrum of Si−3 is presented and discussed. The spectrum shows well-resolved vibrational structure. A comparison with several ab initio calculations shows that the spectrum is due to transitions to the 3A′2 (D3h) state of Si3. The symmetric stretch and degenerate e′ frequencies for the Si3 3A′2 state are determined to be 501±10 and 337±10 cm−1, respectively. Additional structure observed in the spectrum suggests that the negative ion is a fluxional, Jahn–Teller distorted species. The ZEKE spectrum shows no evidence for transitions to the 1A1 state of the neutral, which is predicted to lie very close to the 3A′2 state. A comparison of the ZEKE and previously obtained photoelectron spectrum of Si−3 suggests that these two states are close in energy, but that transitions to the singlet state are very weak in the ZEKE spectrum.