Excited electronic states of the SiF2 radical studied by resonance enhanced multiphoton ionisation spectroscopy and by ab initio methods

✍ Scribed by Russell D. Johnson III; Jeffrey W. Hudgens; Michael N.R. Ashfold

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 504 KB
• Volume: 261
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(96)00990-6

✦ Synopsis

SiF 2 radicals have been produced by the gas-phase reaction of Sill 4 with F atoms in a flow reactor and detected by mass-resolved resonance enhanced multiphoton ionisation (REMPI) spectroscopy. Two band systems are observed. One, a series of one-photon resonances in the wavelength range 210-230 nm, we associate with the previously documented A~B 1 ,--X IA 1 transition. The observed long progression in the excited state bending mode, v 2, reflects the increase in equilibrium bond angle that accompanies this electronic transition. We also identify three two-photon resonances in the wavelength range 315-325 nm. Two we can definitely associate with the B 1B 2 ~ X ~Aj transition. Polarisation studies show the third resonance to involve an excited state of IA 1 symmetry. Guided by the results of companion ab initio calculations we present evidence for and against assignment of this feature as the (vibronically induced) B ~ X 3~ band, or as a hitherto unidentified IA i ~ ~ 1A 1 electronic origin. The calculations also enable prediction of the term values of a further eight, as yet unobserved, excited states of SiF 2.