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NIST Atomic Spectra Database
Ionization Energies Data

He (all spectra)
2 Data Rows Found 

Example of how to reference these results:
Kramida, A., Ralchenko, Yu., Reader, J., and NIST ASD Team (2018). NIST Atomic Spectra Database (ver. 5.6.1), [Online]. Available: https://physics.nist.gov/asd [2019, August 21]. National Institute of Standards and Technology, Gaithersburg, MD. DOI: https://doi.org/10.18434/T4W30F
BibTex Citation (new window)
 

 At. Num.   El.  name   Isoel.  Seq.   Ground  Shells   Ground  Level   Ionization  Energy 
 (eV) 
Uncertainty
 (eV) 
 References 
Helium  He  1s2   1S0    24.58738880                 0.00000015   L17714 
Helium  1s   2S1/2    (54.4177650)                 0.0000003    L7188c95 

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

[ASD Home][Lines Query][Levels Query][List of Spectra][Ground States and Ionization Energies][Bibliography][Help] NIST Physical Measurement Laboratory