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National Institute of Standards and Technology NIST Physical Measurement Laboratory
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 (2014). NIST Atomic Spectra Database (ver. 5.2), [Online]. Available: http://physics.nist.gov/asd [2014, October 24]. National Institute of Standards and Technology, Gaithersburg, MD.
BibTex Citation (new window)
 

 At. Num.   El.  name   Isoel.  Seq.   Ground  Shells   Ground  Level   Ionization  Energy a 
 (eV) 
 References 
Helium  He  1s2   1S0    24.587387936(25)            L17714 
Helium  1s   2S1/2    (54.41776311(2))             L7188c95 
Notes:
Uncertainty is given in parentheses after the value. It is expressed in the units of the last decimal place of the value.

Query time: 0.1 sec

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