The electronic absorption spectrum of N3mdash;in solution was investigated. For this purpose environmental effects on this spectrum were studied, and the thermodynamic properties of the I2sngbnd;N3mdash;complex were determined. In the 190ndash;300hyphen;mmgr; region the spectrum consists of at least three bands, designated byA, B,andC.Their identification is based on the comparison with the spectra of solid alkali azides. BandAwhich is of moderate intensity (egr;sim;400 liter molemdash;1cmmdash;1) appears at 230 mmgr; and is assigned to1Dgr;ularr;1Sgr;g+transition. BandBwith lgr;maxat about 200 mmgr; originates from a charge transfer to the solvent (CTTS). For Band C, the peak of which is at the vacuum uv, a1Sgr;u+excited state is suggested.The nature of the CTTS state of N3mdash;is discussed and evidence is provided for the mixing of this state with the1Dgr;ustate. The investigation of the CTTS band leads to a value for the electronhyphen;affinityE(N3)=81 kcal. One method for deriving this value is based entirely on solvent effects by means of a method which was recently developed. This method yields also an estimate of the crystallographic radius of the ion:R(N3mdash;)sim;1.92 Aring;.
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