Radical-ion generation and trapping in neon matrices at 4 K. Electron spin resonance investigations of F2CO± and C +2

Abstract

Radical-ion e.s.r. studies in neon matrices are summarized briefly and new results are presented for ^12,13C⁺₂(X ⁴Σ) and F₂CO^–, with a tentative assignment for F₂CO⁺. These examples illustrate the flexibility of the neon matrix-deposition method in trapping volatile as well as refractory ion radicals in an inert environment at 4 K. A pulsed-laser vaporization procedure combined with photoionization was used to generate C⁺₂ from ¹²C and ¹³C graphite targets. The electronic ground state determined for C⁺₂ in this e.s.r. study agrees with recent assignments from electronic measurements. The F₂CO^– anion appears to be a carbon-centred radical based on the properties of its ¹³C A tensor, which has a large A_iso value of 715 MHz. The anion, which is isoelectronic to CF₃, deviates from C_2v symmetry, and the magnetic inequivalency of its ¹⁹F nuclei complicates the e.s.r. spectrum. The observed A tensors for ¹⁹F and ¹³C are compared with calculated values conducted at various levels of theory. The F₂CO^– radical was generated by two independent methods, electron addition to F₂CO(g) by photoionization and the codeposition of F₂CO(g) with Na(g) into neon and argon matrices.