Mössbauer effect in molecular iodine crystals

The Mössbauer effect of the 26.8-keV transition in I129 has been studied in molecular iodine crystals. From the quadrupole splitting of the transitions the ratio Q26.8Qgnd, the quadrupole coupling e2qQgnd, and the isomer shift are derived. The sign of the quadrupole coupling shows that the sign of the iodine field gradient is positive. From the isomer shift of I2 and from those of alkali iodides a linear dependence of the isomer shift on the number of p holes is derived. The intensities of the peaks give a strong indication of an angular dependence of the recoilless fraction f(). The D of the I2 crystal, as well as that of the KI crystal, are derived from the temperature dependence of the recoilless fraction.