Characterization of ground states of ^243,244Np

As a part of our long-continuing investigations of low-lying level structures of odd-odd actinides we report here the results of our study on the level structures of transuranic n-rich Z=93 isotopes, namely ²⁴³Np and ²⁴⁴Np. The primary motivation for the present study originates from the critical evaluation and incisive remarks by the respective Nuclear Data Sheets (NDS) evaluators, highlighting the inconclusive, and often contradictory, suggested configuration assignments even to the ground state (gs) of these two Np isotopes. Specifically, the NDS2014 evaluators list j=5/2 from systematics for the gs of ²⁴³Np with both possibilities for the parity. Taking note of this contradictory 5/2⁺ or 5/2^- assignment for the ²⁴³Np core constituent of the doubly odd ²⁴⁴Np, the NDS2017 evaluator considers information on ²⁴⁴Np gs as 'tentative'. The present study aims at finding definitive configuration assignment in each case following a careful and detailed examination of updated available information coupled with results from various criteria including experimental, theoretical and systematics data