Mossbauer Spectroscopic Studies Of Np-237 In Frozen Nitric Acid Solution

We applied Mossbauer spectroscopy to Np-237 in nitric acid solutions to study chemical states. Sample solutions were adjusted to 50 mg/ml of Np(V) and Np(VI) concentration in 0.6 M nitric acid solutions. These solutions were put into original designed containers for samples and mounted to sample holders. The values of isomer shift (IS, relative to NpAl2) of Np(V) and Np(VI) in 0.6 M nitric acid were -17.4(1) and -37.2(3) minis at about 10 K, respectively. It was found that Np(V) had 7 coordination number and Np(VI) had 8 in nitric acid solutions from values of IS.