Studies with the Mössbauer Effect of the Formation of Xenon Bromides in Beta Decay

Abstract

The reaction IBr2−129→βXeBr2129 has been observed for a pure sample of the potassium salt by use of the Mössbauer effect of the 39.48-keV gamma ray of 129Xe. With the assumption of pσ bonding, the quadrupole splitting leads to a value of 0.41 electron transferred to each Br. This is to be compared with 0.52 to each Cl in XeCl2 and 0.72 to each F in XeF2. An impure KIBr2 source shows a qualitatively different velocity spectrum—either due to a distribution of unknown xenon halides or to a molecular rearrangement observed in the act of occurring. If the latter is correct, the linewidth gives a mean life τm ≈ 3.5 × 10−10sec for the rearrangement. A source of CsIBr2 gives a broad singlet spectrum with no trace of XeBr2. The line represents either atomic xenon or a cubic rearrangement product such as XeBr64− or XeBr42−. Evidence from data on recoilless fraction and isomer shifts somewhat favors atomic xenon as the product but is not completely conclusive.