Nuclear data sheets for A=166

Nuclear structure data pertaining to all known A=166 nuclides (Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt) have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation for A=166 supersedes the previous publication (E.N. Shurshikov and N.V. Timofeeva, Nuclear Data Sheets 67, 45 (1992) (literature cutoff date 1 October 1990)) and the revision by C.M. Baglin of W-166 (literature cutoff date 16 April 2000). It includes literature available by 1 March 2008. Subsequent to the previous evaluation, Gd-166 has been observed for the first time and the first observations of excited states in Tb-166, Re-166, Os-166 and Ir-166 have been reported; also, knowledge of collective structure in Dy-166, Ho-166, Er-166, Tm-166, (166)yb, Lu-166, Hf-166, and Ta-166 has been considerably expanded. However, the structure suggested here for Re-166 is highly tentative and a further, more detailed study of a decay into (and out of) Re-166 could be informative.