The far ultra-violet spectra of some 1-iodoalkanes

The far ultra-violet spectra of a series of 1-iodoalkanes (C n H2n+1I, n = 1–6) between 30 000 and 90 000 cm-1 are presented. The spectra are very similar and all the discrete bands are assigned to transitions involving non-bonding electrons localized on the iodine atom. The low energy A bands are assigned to intravalence σ* ←n transitions. At least five Rydberg series are observed, each leading to one of the first two ionization potentials (E 1/2 and E 3/2 ionic states under C 3v symmetry). Comparison of the vibrational structuree of the B, C, D and E bands with that of the photoelectron spectra suggests that these are Rydberg states. Moreover, comparison of the term values with those of the spectrum of xenon, the ‘semi-united’ atom, along with relative intensities, allows assignment of the most intense Rydberg series, including the C and D bands, to ns series. The remaining Rydberg series leading to each ionization potential are then assigned to nd series although an np assignment cannot be ruled out.