On the energy of the 3.5-eV level in 229Th

Abstract

Values determined in several studies for the first isomeric state of 229Th as 3.5(10), 3.4(18), 5.5(10), and 7.6(5) eV differ markedly from one another. A comparison of the first two studies that was performed in the present article indicates that there is a systematic error in the energies of the transitions in 229Th. It is shown that each of the first two values is dependent on the placement or energy of only one transition (or on both of these two factors). The third value, that of 5.5(10) eV, is not independent, since it is a result of rather complicated calculations for the scheme of energy levels in 229Th with allowance for the first two studies. It is shown that the accuracy in determining the error in 7.6(5) eV is likely to be exaggerated. It is concluded that the energy of the 3.5-eV state ranges between 0 and 15 eV.