Nuclear Data Sheets for A=244

Abstract

Available information pertaining to the nuclear structure of ground and excited states for all known nuclei with mass numbers A=244 have been compiled and evaluated. The adopted level and decay schemes, as well as the detailed nuclear properties and configuration assignments based on experimental data are presented for these nuclides. When there are insufficient data, expected values from systematics of nuclear properties and/or theoretical calculations are quoted. Unexpected or discrepant experimental results are also noted. Information provided in 244U is tentative as it is from the possible production in the study of 1960Di03 of debris of the first large-scale thermonuclear test (Ivy Mike) of November 1, 1952 in the Pacific Ocean. No new experimental data are available for 244Np with the information for g.s Jπ considered tentative. Experimental work is needed for 244Np as theoretical work and systematics along with the Gallagher-Moszkowski rules that suggest either Jπ=2+ or 7−. Jπ = (7−) g.s has been considered by the evaluator due to population of high spin states in the beta decay study. In 244Pu, a new K isomer was identified and in addition rotational bands built on the isomer have been observed via the deep inelastic excitation. However, there has been no new measurements since the last evaluation to determine the ratio of the energy levels of the first 4+ state to the first 2+ state (E4+/E2+) in 244Pu that showed a discrepancy from a typical value of 3.333. In the current evaluation, the evaluator has considered the 110γ measured in the 244Np β-decay questionable. Further research into the determination of the gammas depopulating these levels is necessary. In 244Am, specifically the (d,p) transfer reaction and in the (n, γ) secondary γ's, there are a large number of gammas that are unplaced. Since its last measurement in 1966, the electron capture dataset has been updated with a tentative partial level scheme for 244Cm which also provided a new half-life measurement for 244Bk. In 244Fm, a fusion evaporation experiment measured the half-life and provided upper limits for the SF, α decay, and ε branching. A summary and compilation of the discovery of various isotopes in this mass region is given in 2013Fr02 (244Np, 244Pu, 244Am, 244Cm, 244Bk, and 244Cf), 2011Me01 (244Es), and 2013Th02 (244Fm). This work supersedes the 2003 evaluation by Y.A. Akovali (2003Ak04).