Probing the molecular structure of aqueous triiodide via X-ray photoelectron spectroscopy and correlated electron phenomena

Abstract

Liquid-microjet-based X-ray photoelectron spectroscopy was applied to aqueous triiodide solutions, I3(aq.)-, to investigate the anion's valence- and core-level electronic structure, ionization dynamics, associated electron-correlation effects, and nuclear geometric structure. The...

Spontaneous Appearance of Triiodide Covering the Topmost Layer of the Iodide Solution Interface Without Photo-Oxidation

“…Liquid jet X-ray photoelectron spectroscopy is another powerful tool to probe surface composition, but this technique may give different results compared to this SFG study, as in the liquid jet, the surface is generated quasi-instantaneously, and we expect the generation of I 3 − to be slower than the time scale of the surface generation in these types of experiments. 35,38 ■ ENVIRONMENTAL IMPLICATIONS Here, by combining PD-HD-SFG spectroscopy with AIMD simulation, we confirmed that the iodide ion does not significantly reduce the contact area of the N 2 gas−water interface; iodide ions are instead located below the topmost water layer. When the iodide ion concentration increases, the triiodide ions are more present at the vapor−water interface, resulting in a ∼10 8 times higher concentration at the surface than in bulk.…”

Solvent-Dependent Structural Dynamics in the Ultrafast Photodissociation Reaction of Triiodide Observed with Time-Resolved X-ray Solution Scattering

“…32−35 A model system which has been utilized to observe ultrafast bond cleavage and recombination has been the photodissociation of triiodide, I 3 − + hν → I 2 − + I. 36−39 Due to its seemingly simple dissociation reaction involving only three solute atoms, it has been extensively investigated using a manifold of techniques, including absorption, 36,39,40 Raman, 41 and photoelectron spectroscopy 42 as well as TR-XSS 43 and electron diffraction. 44 The photodissociation of I 3 − (I 3 − → I 2 − + I) takes place upon photoexcitation into one of the two broad absorption bands centered around 290 and 360 nm (Figure S1).…”

“…The former describes the recombination of fragments directly inside the first layer of solvent molecules within a few picoseconds. In secondary geminate recombination, the fragments are separated by a few layers of solvent molecules, also referred to as “contact pair”, leading to recombination on tens to hundreds of picoseconds. − A model system which has been utilized to observe ultrafast bond cleavage and recombination has been the photodissociation of triiodide, I 3 – + h ν → I 2 – + I. − Due to its seemingly simple dissociation reaction involving only three solute atoms, it has been extensively investigated using a manifold of techniques, including absorption, ,, Raman, and photoelectron spectroscopy as well as TR-XSS and electron diffraction …”

“…Spectroscopic studies showed features from asymmetric vibrations of I 3 – in protic solvents while these were not visible in apolar solvents. ,− Later structural studies using X-ray techniques and molecular dynamics simulations demonstrated that the bending angle and bond lengths of I 3 – depend on the surrounding solvent. − However, these studies did not reach agreement in terms of the molecular structure of ground state triiodide, showing varying bond distances and bending angles. The exact ground state structures are hence still a topic of discussion. , …”

“…The exact ground state structures are hence still a topic of discussion. 42,43 Most recently, two studies of the I 3 − → I 2 − + I reaction in solution utilizing ultrafast scattering techniques with subpicosecond time resolution have emerged. In a pioneering study, 44 Ledbetter et al utilized liquid-phase ultrafast MeV electron diffraction with ∼180 fs time resolution (fwhm) to estimate the dissociation speed following the photoexcitation event and found this to be around v diss.…”