Studies of IBr, ICl, and I2Cl6 Crystal Properties by Means of the Mössbauer Effect in 129I. I. Chemical Bonds

Using ¹²⁹I as Mössbauer nucleus, the properties of ICl, IBr, and I₂Cl₆, as well as I₂Cl₄Br₂, were investigated. From the well‐resolved spectra of the quadrupole splitting, the $e^2\mathrm{qQ}$ , the $\eta$ parameter, and the isomer shift with respect to the standard ⁶⁶Zn¹²⁹Te source are derived. These data are used to deduce the $\text{5p}$ electron population of I. On the basis of the sensitivity of the isomer shift to the $s$ character of the bond, it is shown that no $\mathrm{sp}$ hybridization occurs. The linear dependence of the isomer shift on the $p$ holes is found to extend to $h_p$ values higher than 1. A relationship is derived to include $h_s$ as well as $h_p$ when iodine is in a high valence state.