Far ultraviolet solution spectroscopy of the iodide ion
Abstract
The far ultraviolet absorption spectra of iodide ion have been studied in a large range of solvents and over a large temperature range. These include both strong blue- and red-shifting solvents relative to water and D2O. A number of new absorption bands have been observed, in some cases down to 165 nm. The observed absorption spectra are envelopes composed of overlapping absorption bands which have been resolved, using mainly lognormal (asymmetric) band shapes, to show sets of band pairs labelled A1/A2, B1/B2etc. The first characteristic charge-transfer-to-solvent (c.t.t.s.) doublet, A1/A2, has a separation close to the doublet splitting of the 2P atomic states of the iodine radical in the gas phase. The B1B2 higher energy doublet bands have a slightly smaller separation and have c.t.t.s. character such as high solvent and temperature sensitivities. At higher energies further bands are observed. The band systems observed have been correlated on the basis of solvent shifts, doublet band splittings, oscillator strengths and temperature coefficients. The c.t.t.s. character of the higher energy bands has been evaluated and tentative assignments suggested.