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Ref. ID |   |   |   | 
Reference |   |  
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| BBBL98  | S. D. Bergeson, A. Balakrishnan, K. G. H. Baldwin, T. B. Lucatorto, J. P. Marangos, T. J. McIlrath, T. R. O'Brian, S. L. Rolston, C. J. Sansonetti, J. Wen, N. Westbrook, C. H. Cheng, and E. E. Eyler, Phys. Rev. Lett. 80, 3475 (1998).    |  
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| BDD72   | H. G. Berry, J. Desesquelles, and M. Dufay, Phys. Rev. A 6, 600 (1972).    |  
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| BM00    | J. Baker and P. Mohr, unpublished calculations (2000).    |  
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| D03     | G. W. F. Drake, calculated energies for He I levels (2003), to be published in Can. J. Phys. These data comprise a revision of Table 11.7 of [D96]. |  
|   |   |  
| D96     | G. W. F. Drake, High Precision Calculations for Helium, in Atomic Molecular, & Optical Physics, G.W.F. Drake, Ed. (American Inst. of Physics, Woodbury, New York, 1996), pp. 154-171.    |  
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| DM98    | G. W. F. Drake and W. C. Martin, Can. J. Phys. 76, 679 (1998).    |  
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| EUVH97  | K. S. E. Eikema, W. Ubachs, W. Vassen, and H. Horgovorst, Phys. Rev. A 55, 1866 (1997).    |  
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| FW96    | J. R. Fuhr and W. L. Wiese, NIST Atomic Transition Probability Tables, CRC Handbook of Chemistry & Physics, 77th Edition, D. R. Lide, Ed., CRC Press, Inc., Boca Raton, FL (1996).    |  
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| GM65    | J. D. Garcia and J. E. Mack, J. Opt. Soc. Am. 55, 654 (1965).    |  
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| L70a    | U. Litzén, Phys. Scr. 2, 103 (1970).    |  
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| M02     | W. C. Martin, ongoing compilation of data for He I (2002). This work includes an updating of the energy-level data in [M87].  The uncertainty of the excited-level system and limit with respect to the ground level is about 0.002 cm-1 [EUVH97, BBBL98].  References for most of the more recent experimental data are given in [DM98].  Some level separations are known to six or more decimal places, but have here been rounded to four places.  The values for some levels are derived from recent theoretical calculations [D03].  The wavelengths are calculated from the energy levels.  The estimated uncertainty of the wavelengths of the resonance lines given to five places (507-591 Å) is at most one unit in the fifth place. |  
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| M60a    | W. C. Martin, J. Res. Natl. Bur. Stand. (U.S.) 64A, 19 (1960).    |  
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| M87     | W. C. Martin, Phys. Rev. A 36, 3575 (1987).    |  
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| MK00b   | P. Mohr and S. Kotochigova, unpublished calculations (2000). Several weaker fine-structure components for the He II multiplet at 4685 Å have been omitted here. |  
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| TW71    | J. L. Tech and J. F. Ward, Phys. Rev. Lett. 27, 367 (1971).    |  
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