Muon radiative energy loss (in 1.0E06 cm^2/g) in Neptunium with Z = 93, A = [237.04817(2)] (f12.0,4f12.4) E (GeV) b_brem b_pair b_nucl b_total 2. 2.1548 0.2886 0.3582 2.8016 5. 2.9952 1.9755 0.3823 5.3530 10. 3.6821 3.2882 0.3749 7.3452 20. 4.3871 4.4900 0.3617 9.2389 50. 5.3085 6.3357 0.3469 11.9911 100. 5.9623 7.5502 0.3400 13.8525 200. 6.5575 8.6231 0.3367 15.5173 500. 7.2229 9.6023 0.3369 17.1622 1000. 7.6217 10.1192 0.3421 18.0830 2000. 7.9306 10.4908 0.3503 18.7717 5000. 8.2157 10.8008 0.3652 19.3817 10000. 8.3561 10.9435 0.3801 19.6797 20000. 8.4488 11.0366 0.3973 19.8827 50000. 8.5316 11.1055 0.4243 20.0613 100000. 8.5590 11.1343 0.4473 20.1406