Wavelengths, Transition Probabilities, and Energy Levels for the Spectra of Cesium „Cs I –Cs LV… … J. E. Sansonettia National Institute of Standards and Technology, Gaithersburg, Maryland 20899 ͑Received 21 April 2009; accepted 21 April 2009; published online 29 October 2009͒ Energy level values, with designations and uncertainties, have been compiled for the spectra of the neutral atom and all positive ions of cesium ͑Z=55͒. Transition wave- lengths with classifications, intensities, and transition probabilities are also tabulated. In addition, ground states, ionization energies, and hyperfine structure constants are listed. For most ionization stages experimental data are available; however, for those for which only theoretical calculations or fitted values exist, these are reported. There are a few ionization stages for which only a calculated ionization potential is available. © 2009 by the U.S. Secretary of Commerce on behalf of the United States. All rights reserved. ͓doi:10.1063/1.3132702͔ CONTENTS 6.26. Cs XXVI............................. 874 6.27. Cs XXVII............................. 877 6.28. Cs XXVIII............................ 878 1. Introduction.............................. 762 6.29. Cs XXIX............................. 880 2. Wavelength Tables. ....................... 762 6.30. Cs XXX.............................. 881 3. Energy Level Tables....................... 763 6.31. Cs XXXI............................. 882 4. Uncertainties and Significant Figures.......... 763 6.32. Cs XXXII............................. 882 5. References for the Introduction. ............. 764 6.33. Cs XXXIII............................ 882 6. Ionization Stages. ......................... 764 6.34. Cs XXXIV............................ 882 6.1. Cs I................................. 764 6.35. Cs XXXV............................. 883 6.2. Cs II................................ 777 6.36. Cs XXXVI............................ 883 6.3. Cs III............................... 815 6.37. Cs XXXVII............................ 883 6.4. Cs IV................................ 837 6.38. Cs XXXVIII........................... 884 6.5. Cs V................................ 843 6.39. Cs XXXIX............................ 884 6.6. Cs VI................................ 847 6.40. Cs XL............................... 886 6.7. Cs VII............................... 849 6.41. Cs XLI............................... 890 6.8. Cs VIII.............................. 855 6.42. Cs XLII.............................. 893 6.9. Cs IX................................ 859 6.43. Cs XLIII.............................. 895 6.10. Cs X................................ 862 6.44. Cs XLIV............................. 898 6.11. Cs XI................................ 865 6.45. Cs XLV.............................. 900 6.12. Cs XII............................... 870 6.46. Cs XLVI............................. 902 6.13. Cs XIII.............................. 870 6.47. Cs XLVII............................. 906 6.14. Cs XIV.............................. 871 6.48. Cs XLVIII............................ 910 6.15. Cs XV............................... 871 6.49. Cs XLIX............................. 911 6.16. Cs XVI.............................. 871 6.50. Cs L................................ 913 6.17. Cs XVII.............................. 871 6.51. Cs LI................................ 913 6.18. Cs XVIII............................. 871 6.52. Cs LII............................... 915 6.19. Cs XIX.............................. 872 6.53. Cs LIII............................... 916 6.20. Cs XX............................... 872 6.54. Cs LIV............................... 918 6.21. Cs XXI.............................. 873 6.55. Cs LV............................... 919 6.22. Cs XXII.............................. 873 7. Acknowledgments......................... 920 6.23. Cs XXIII............................. 873 8. References............................... 920 6.24. Cs XXIV............................. 874 6.25. Cs XXV.............................. 874 List of Tables ͒ a Electronic mail: [email protected]. © 2009 by the U.S. Secretary of Commerce on behalf of the United States. 1. Observed spectral lines of Cs I............... 765 All rights reserved. 2. Energy levels of Cs I....................... 771 0047-2689/2009/38„4…/761/163/$45.00761 J. Phys. Chem. Ref. Data, Vol. 38, No. 4, 2009 Downloaded 20 Mar 2013 to 129.6.105.191. Redistribution subject to AIP license or copyright; see http://jpcrd.aip.org/about/rights_and_permissions 762 J. E. SANSONETTI 3. Observed spectral lines of Cs II.............. 778 60. Energy levels of Cs XLIX................... 913 4. Energy levels of Cs II...................... 809 61. Spectral lines of Cs LI...................... 914 5. Observed spectral lines of Cs III.............. 816 62. Energy levels of Cs LI...................... 915 6. Energy levels of Cs III...................... 834 63. Spectral lines of Cs LII..................... 915 7. Observed spectral lines of Cs IV.............. 837 64. Energy levels of Cs LII..................... 916 8. Energy levels of Cs IV..................... 841 65. Spectral lines of Cs LIII..................... 917 9. Observed spectral lines of Cs V.............. 844 66. Energy levels of Cs LIII..................... 917 10. Energy levels of Cs V...................... 846 67. Spectral lines of Cs LIV..................... 918 11. Observed spectral lines of Cs VI.............. 847 68. Energy levels of Cs LIV.................... 918 12. Energy levels of Cs VI..................... 849 69. Spectral lines of Cs LV..................... 919 13. Observed spectral lines of Cs VII............. 850 70. Energy levels of Cs LV..................... 920 14. Energy levels of Cs VII..................... 853 15. Observed spectral lines of Cs VIII............ 855 1. Introduction 16. Energy levels of Cs VIII.................... 857 17. Observed spectral lines of Cs IX.............. 859 Cesium was discovered in 1861 by Kirchhoff and Bunsen 18. Energy levels of Cs IX..................... 860 ͓61KIR/BUN͔, who named it after the Latin word caesius 19. Observed spectral lines of Cs X.............. 862 ͑meaning sky blue͒ because of the two bright blue lines they 20. Energy levels of Cs X...................... 864 observed when its salts were heated in a flame. It was the 21. Observed spectral lines of Cs XI.............. 866 first element to be discovered spectroscopically. Cesium is 22. Energy levels of Cs XI..................... 868 the most electropositive and alkaline element and it also has 23. Observed spectral lines of Cs XIX............ 872 the lowest ionization energy. It oxidizes rapidly, may ignite 24. Observed spectral lines of Cs XX............. 872 when exposed to air, and reacts explosively with water. It is 25. Energy levels of Cs XX..................... 872 silvery white and soft, with a melting point just above room ؠ 26. Spectral lines of Cs XXIII................... 873 temperature ͑28.4 C͒. Its atomic number is 55; its atomic ؠ 27. Energy levels of Cs XXIII................... 873 mass is 132.9054 amu; its boiling point is 699 C; and its ؠ 28. Spectral lines of Cs XXVI................... 874 specific gravity at 20 C is 1.873 ͓05CRC͔. The most notable 29. Energy levels of Cs XXVI................... 876 use of cesium is in atomic clocks, with the second being 30. Spectral lines of Cs XXVII................... 878 defined as the duration of 9 192 631 770 periods of the ra- 31. Energy levels of Cs XXVII................... 879 diation corresponding to the transition between the two hy- 133 32. Spectral lines of Cs XXVIII.................. 880 perfine levels of the ground state of the Cs atom. 33. Energy levels of Cs XXVIII.................. 880 For this compilation of spectral data of cesium the litera- 34. Spectral lines of Cs XXIX................... 881 ture for each ionization stage has been reviewed and lists of 35. Energy levels of Cs XXIX................... 881 the most accurate wavelengths and energy levels have been 36. Energy levels of Cs XXX.................... 882 assembled. A brief summary of the history of research for 37. Spectral lines of Cs XXXVII.................. 884 each spectrum and details regarding the data included in this 38. Energy levels of Cs XXXVII................. 884 compilation are given. Where available, experimental data 39. Spectral lines of Cs XXXIX.................. 884 are presented; however, where only fitted data or theoreti- 40. Energy levels of Cs XXXIX.................. 885 cally calculated data are available these are included. To 41. Spectral lines of Cs XL..................... 886 clarify which data are not obtained by experimental observa- 42. Energy levels of Cs XL..................... 889 tion, wavelengths, energy levels, and ionization energies that 43. Spectral lines of Cs XLI..................... 890 have been obtained by isoelectronic fitting are indicated by 44. Energy levels of Cs XLI.................... 893 enclosure in square brackets while theoretical values are in- 45. Spectral lines of Cs XLII.................... 893 dicated by enclosure in parentheses. 46. Energy levels of Cs XLII.................... 895 47. Spectral lines of Cs XLIII.................... 896 2. Wavelength Tables 48. Energy levels of Cs XLIII................... 898 49. Observed spectral lines of Cs XLIV........... 899 In the tables of wavelengths the following information is 50. Energy levels of Cs XLIV................... 899 included: 51. Spectral lines of Cs XLV.................... 901 ͑i͒ Wavelengths are reported in units of angstroms,