Author: C.D. Nesaraja |  Citation: Nucl. Data Sheets 130, 183 (2015) |  Cutoff date: 30-Sep-2015 

 Full ENSDF file | Adopted Levels (PDF version) 

Q(β-)=1300 keV 70S(n)= 6130 keV 70S(p)= 5740 keV 70Q(α)= 4310 keV 70
Reference: 2012WA38

General Comments:

Experimental Studies:

1981Pa20: 241Np produced via 238U(α,p) with Eα=32 MeV and 244Pu(n,p3n) with En=30-160 MeV at the Brookhaven MEIN facility. Irradiation was followed by chemical separation. Decay of 241Np was studied by γ spectroscopy, using a high resolution Ge(Li) detector, and by β emission by a 4π proportional counter. Measured T1/2 for 241Np from least squares decay analyses.

1966Qa02: 241Np produced via 238U(α,p) at Nuffield Cyclotron at Birmingham University with Eα=40 MeV. Irradiation was followed by chemical separation. α Geiger counter, anthrracene crystal scintillation β spectrometer, Xe proportional counter, NaI(Tl) detector, and a ZnS-Ag scintillation α counter were used to measure γ and β radiations. The half-life from decay curves for 241Np was 16.0 min 2 with an end-point energy of 1.25 MeV. The 3.4 hour activity reported by 1960Le03 was not detected.

1960Le03:241Np produced via 238U(α,p) at Crocker Laboratory cyclotron with Eα=35 MeV and 48 MeV. Irradiation was followed by chemical and time of flight separation. γγ and βγ coincidences measured with NaI detector. Decay curves identified the 16 min half-life with strong evidence for an isomer with 3.4 hour half-life

1959Va32: 241Np produced via 238U(α,p) at Argonne cyclotron followed by chemical separation and measured with a 2π and end-window proportional counters. β and γ spectrum were measured with the anthracene crystal and a NaI(Tl) detectors. The β spectrum end- point energy of the 16 minute component was 1.36 MeV 10 with logft of 5.8.

Theoretical/Systematical Studies:

2004Pa40: Calculated deformation parameters and the proton one quasiparticle states of heaviest nuclei using the macroscopic-microscopic approach. Systematics as function of of neutron number for odd α isotopes in Np were also calculated

Jπ(level) T1/2(level)
  0.0 5/2+ 13.9 m 2 
% β- = 100

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Additional Level Data and Comments:

  0.05/2+ 13.9 m 2 
% β- = 100
%α<1×10-6 given by 1966Qa02, however no α branch was observed in their study. Using the ALPHAD program, evaluator estimated %α <1.7×10-14 with the assumption HF |>4 for a non-favored transition.

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