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National Institute of Standards and Technology NIST Physical Measurement Laboratory
NIST Atomic Spectra Database
Ionization Energies Data

Ac (all spectra)
89 Data Rows Found 
Example of how to reference these results:
Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (2024). NIST Atomic Spectra Database (ver. 5.12), [Online]. Available: https://physics.nist.gov/asd [2026, October 26]. National Institute of Standards and Technology, Gaithersburg, MD. DOI: https://doi.org/10.18434/T4W30F
BibTex Citation (new window)
 

 Ionization  Energy 
 (cm-1) 
  43 394.52         
  [94 800]           
  [140 630]           
  [361 000]           
  (444 000)           
  (540 000)           
  (637 000)           
  (798 000)           
  (919 000)           
  (1 161 000)           
  (1 299 000)           
  (1 879 000)           
  (2 057 000)           
  (2 250 000)           
  (2 460 000)           
  (2 662 000)           
  (2 863 000)           
  (3 146 000)           
  (3 355 000)           
  (3 581 000)           
  (3 791 000)           
  (4 902 000)           
  (5 167 000)           
  (5 432 000)           
  (5 697 000)           
  (6 314 000)           
  (6 610 000)           
  (7 390 000)           
  (7 690 000)           
  (8 290 000)           
  (8 860 000)           
  (9 440 000)           
  (10 018 000)           
  (10 590 000)           
  (11 170 000)           
  (11 740 000)           
  (12 320 000)           
  (12 970 000)           
  (13 560 000)           
  (14 140 000)           
  (14 700 000)           
  (15 300 000)           
  (15 900 000)           
  (18 535 000)           
  (19 051 000)           
  (19 599 000)           
  (20 188 000)           
  (20 745 000)           
  (21 285 000)           
  (22 277 000)           
  (22 850 000)           
  (23 455 000)           
  (24 035 000)           
  (26 326 000)           
  (26 891 000)           
  (27 495 000)           
  (28 060 000)           
  (30 738 000)           
  (31 399 000)           
  (33 012 000)           
  [33 676 700]           
  (54 580 000)           
  (55 838 000)           
  (57 169 000)           
  (58 596 000)           
  (59 959 000)           
  (61 282 000)           
  (64 121 000)           
  (65 500 000)           
  (67 041 000)           
  (68 436 000)           
  (72 372 000)           
  (73 590 000)           
  (74 921 000)           
  (76 163 000)           
  (84 551 000)           
  (86 019 000)           
  (88 939 000)           
  (90 318 000)           
  (189 371 000)           
  (192 670 000)           
  (196 315 000)           
  (199 671 000)           
  (230 779 000)           
  (235 183 000)           
  (240 789 000)           
  (244 330 000)           
  (967 427 600)           
  (984 505 000)           
Notes:
a Uncertainty of the listed value is unknown.

If you did not find the data you need, please inform the ASD Team.

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