Muon radiative energy loss (in 1.0E06 cm^2/g) in Actinium with Z = 89, A = [227.02775(2)] (f12.0,4f12.4) E (GeV) b_brem b_pair b_nucl b_total 2. 2.0701 0.3360 0.3597 2.7659 5. 2.8760 1.9537 0.3840 5.2137 10. 3.5344 3.2116 0.3765 7.1225 20. 4.2101 4.3685 0.3632 8.9417 50. 5.0935 6.1406 0.3484 11.5824 100. 5.7208 7.3078 0.3413 13.3699 200. 6.2921 8.3400 0.3381 14.9702 500. 6.9315 9.2830 0.3383 16.5527 1000. 7.3151 9.7812 0.3435 17.4398 2000. 7.6126 10.1396 0.3517 18.1039 5000. 7.8874 10.4388 0.3667 18.6930 10000. 8.0230 10.5766 0.3817 18.9813 20000. 8.1125 10.6666 0.3990 19.1781 50000. 8.1864 10.7332 0.4261 19.3457 100000. 8.2191 10.7609 0.4493 19.4292