Nuclear Data Sheets for A = 150

Abstract

Nuclear Data Sheets for A=150 (last compiled in 1964) have been prepared using all pertinent experimental information from more than 300 papers (received prior to March 1975). Some information is now available for 11 elements, from Ce through Er. This mass chain is of particular interest since it lies in a region of transition from spherical to deformed nuclei; sufficient J π-information is available for Sm to enable a meaningful comparison of its low-lying bands of levels with those of nearby nuclei. Less extensive level schemes now exist for Gd (about 40 levels, 7 firm J π-assignments) and Nd (10 levels, 3 firm J π-assignments). The 4 states postulated on the basis of γ-cascades in each of Ce and Dy require verification. In the odd-mass A=150 nuclei (Pr, Pm, Eu, Tb, Ho) only one excited state has been identified (in Tb) apart from isomeric states. Isomers exist for Eu, Tb and possibly Ho, but the excitation energy is unknown in each case so it is not clear which long-lived state is the ground state, although most authors assume low-spin Eu and Tb to represent the ground state. Spin measurements for Pr, Pm, Tb and Ho ground states and Eu and Tb isomeric states are needed since shell-model systematics do not give reliable predictions in this mass region and (β + + ε)-decay does not generate definite assignments. T ½ ≈ 34 y is now adopted for high-spin Eu, and the possible existence of a third long-lived state of Eu (to explain earlier data giving T ½ ≈ 6 y for the former state) is presently under investigation by J. Mihelich. The adopted value of Q + for 3-h Tb (based on experimental E β ) disagrees with the value in the current mass table, presumably because the latter assumes that 3-h Tb (J=2?) a-decay populates the 4 − ground state of 146Eu. Despite the volume of Sm(n, γ) data available, the majority of transitions remain unplaced, and a number of unresolved doublets presumably persist. [Extensive, Ge(Li) detector coincidence data would probably resolve many existing ambiguities.] Separate experiments yield inconsistent intensities for a number of weak ce-lines. Because of space limitations, theoretical conversion coefficients used to deduce multipolarities for Sm and Gd transitions are not shown but are available from the authors upon request. Note that 3-h Tb, 34-y Eu, and 40-s Ho decay schemes and much of the Nd level scheme are based on presently unpublished data. The following is a partial list of papers pertaining to A=150 nuclei, but containing no new experimental data for those nuclei: Ce: 71Ge15, 72Wi15, 73Fl02; Dy: 60To05, 64Ma17; Eu: 60To05; Gd: 60To05, 72Hs07; Nd: 65So04, 70Se18, 70Va22, 72Ab18, 72Br61, 72Ru08, 73Ab06, 73Gu09, 73Le19, 73Me05, 73Me08, 73Pr14, 73Pr19, 73To15, 74Ca05, 74En08; Pm: 60To05; Sm: 65Le23, 68Lu12, 69Ca02, 70Be72, 70Ra28, 70Ru05, 70Sc35, 70Se18, 70So02, 71Be95, 71Dz04, 71Ku32, 71Ta27, 72BaC7, 72BeA2, 72Ko58, 72Ma17, 72Wi15, 73Bu30, 73Gu09, 73Pe15, 73Pr14, 73Sa14, 73Si25, 74Ca05, 74Ja13, 74Kr16, 74Ku14, 74Le26; Tb: 60To05, 72Ar36.