Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Atom-at-a-time laser resonance ionization spectroscopy of nobelium


Optical spectroscopy of a primordial isotope has traditionally formed the basis for understanding the atomic structure of an element. Such studies have been conducted for most elements1 and theoretical modelling can be performed to high precision2,3, taking into account relativistic effects that scale approximately as the square of the atomic number. However, for the transfermium elements (those with atomic numbers greater than 100), the atomic structure is experimentally unknown. These radioactive elements are produced in nuclear fusion reactions at rates of only a few atoms per second at most and must be studied immediately following their production4, which has so far precluded their optical spectroscopy. Here we report laser resonance ionization spectroscopy of nobelium (No; atomic number 102) in single-atom-at-a-time quantities, in which we identify the ground-state transition 1S0 1P1. By combining this result with data from an observed Rydberg series, we obtain an upper limit for the ionization potential of nobelium. These accurate results from direct laser excitations of outer-shell electrons cannot be achieved using state-of-the-art relativistic many-body calculations5,6,7,8 that include quantum electrodynamic effects, owing to large uncertainties in the modelled transition energies of the complex systems under consideration. Our work opens the door to high-precision measurements of various atomic and nuclear properties of elements heavier than nobelium, and motivates future theoretical work.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Resonance ionization signals of nobelium atoms.
Figure 2: Saturation characteristics of the first-step resonance for 254No.
Figure 3: Observed high-lying Rydberg states in nobelium.


  1. 1

    NIST ASD Team. Atomic Spectra Database version 5.3, (NIST, accessed March 2016)

  2. 2

    Eliav, E., Fritzsche, S. & Kaldor, U. Electronic structure theory of the superheavy elements. Nucl. Phys. A 944, 518–550 (2015)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Schwerdtfeger, P., Pašteka, L. F., Punnett, A. & Bowman, P. O. Relativistic and quantum electrodynamic effects in superheavy elements. Nucl. Phys. A 944, 551–577 (2015)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Backe, H., Lauth, W., Block, M. & Laatiaoui, M. Prospects for laser spectroscopy, ion chemistry and mobility measurements of superheavy elements in buffer-gas traps. Nucl. Phys. A 944, 492–517 (2015)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Indelicato, P., Santos, J. P., Boucard, S. & Desclaux, J.-P. QED and relativistic corrections in superheavy elements. Eur. Phys. J. D 45, 155–170 (2007)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Borschevsky, A. et al. Predicted spectrum of atomic nobelium. Phys. Rev. A 75, 042514 (2007)

    ADS  Article  Google Scholar 

  7. 7

    Liu, Y., Hutton, R. & Zou, Y. Atomic structure of the super-heavy element No I (Z = 102). Phys. Rev. A 76, 062503 (2007)

    ADS  Article  Google Scholar 

  8. 8

    Dzuba, V. A., Safronova, M. S. & Safronova, U. I. Atomic properties of superheavy elements No, Lr, and Rf. Phys. Rev. A 90, 012504 (2014)

    ADS  Article  Google Scholar 

  9. 9

    Worden, E. F., Blaise, J., Fred, M., Trautmann, N. & Wyart, J.-F. in The Chemistry of the Actinide and Trans-actinide Elements Vol. 3 (eds Morss, L. R. et al.) Ch. 16.4 (Springer, 2008)

    Google Scholar 

  10. 10

    Sewtz, M. et al. First observation of atomic levels for the element fermium (Z = 100). Phys. Rev. Lett. 90, 163002 (2003)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Sewtz, M. et al. Resonance ionization spectroscopy of fermium (Z = 100). Spectrochim. Acta B 58, 1077–1082 (2003)

    ADS  Article  Google Scholar 

  12. 12

    Backe, H. et al. Laser spectroscopic investigation of the element fermium (Z = 100). Hyperfine Interact. 162, 3–14 (2005)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Nagame, Y., Kratz, J. V. & Schädel, M. Chemical studies of elements with Z ≥ 104 in liquid phase. Nucl. Phys. A 944, 614–639 (2015)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Türler, A., Eichler, R. & Yakushev, A. Chemical studies of elements with Z ≥ 104 in gas phase. Nucl. Phys. A 944, 640–689 (2015)

    ADS  Article  Google Scholar 

  15. 15

    Sato, T. K. et al. Measurement of the first ionization potential of lawrencium, element 103. Nature 520, 209–211 (2015)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Lauth, W. et al. Resonance ionization spectroscopy in a buffer gas cell with radioactive decay detection, demonstrated using 208Tl. Phys. Rev. Lett. 68, 1675–1678 (1992)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Backe, H. et al. Towards optical spectroscopy of the element nobelium (Z = 102) in a buffer gas cell. Eur. Phys. J. D 45, 99–106 (2007)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Letokhov, V. S. Laser Photoionization Spectroscopy (Academic Press, 1987)

  19. 19

    Backe, H. et al. Isotope shift measurements for superdeformed fission isomeric states. Phys. Rev. Lett. 80, 920–923 (1998)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Backe, H. et al. Stability of superdeformation for americium fission isomers as function of the neutron number. Nucl. Phys. A 690, 215–218 (2001)

    ADS  Article  Google Scholar 

  21. 21

    Laatiaoui, M. et al. On laser spectroscopy of the element nobelium (Z = 102). Eur. Phys. J. D 68, 71–77 (2014)

    ADS  Article  Google Scholar 

  22. 22

    Hofmann, S. & Münzenberg, G. Discovery of the heaviest elements. Rev. Mod. Phys. 72, 733–767 (2000)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Lautenschläger, F. et al. Developments for resonance ionization laser spectroscopy of the heaviest elements at SHIP. Nucl. Instrum. Methods B 383, 115–122 (2016)

    ADS  Article  Google Scholar 

  24. 24

    Fritzsche, S. On the accuracy of valence-shell computations for heavy and super-heavy elements. Eur. Phys. J. D 33, 15–21 (2005)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Martin, W. C. Series formulas for the spectrum of atomic sodium (Na I). J. Opt. Soc. Am. 70, 784–788 (1980)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Wendt, K., Gottwald, T., Mattolat, C. & Raeder, S. Ionization potentials of the lanthanides and actinides — towards atomic spectroscopy of super-heavy elements. Hyperfine Interact. 227, 55–67 (2014)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Campbell, P., Moore, I. D. & Pearson, M. R. Laser spectroscopy for nuclear structure physics. Prog. Part. Nucl. Phys. 86, 127–180 (2016)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Herzberg, R.-D. et al. Nuclear isomers in superheavy elements as stepping stones towards the island of stability. Nature 442, 896–899 (2006)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Sugar, J. Revised ionization energies of the neutral actinides. J. Chem. Phys. 60, 4103 (1974)

    ADS  CAS  Article  Google Scholar 

  30. 30

    Oganessian, Yu . Ts. et al. Measurements of cross sections for the fusion-evaporation reactions 204,206,207,208Pb + 48Ca and 207Pb + 34S: decay properties of the even-even nuclides 238Cf and 250No. Phys. Rev. C 64, 054606 (2001)

    ADS  Article  Google Scholar 

  31. 31

    Kindler, B. et al. Chemical compound targets for SHIP on heated carbon backings. Nucl. Instrum. Methods A 561, 107–111 (2006)

    ADS  CAS  Article  Google Scholar 

  32. 32

    Laatiaoui, M. et al. Perspectives for laser spectroscopy of the element nobelium. Hyperfine Interact. 227, 69–75 (2014)

    ADS  CAS  Article  Google Scholar 

  33. 33

    Sulignano, B. et al. Identification of a K isomer in 252No. Eur. Phys. J. A 33, 327–331 (2007)

    ADS  CAS  Article  Google Scholar 

Download references


We thank the staff of the GSI ion source and accelerator for the preparation of a stable 48Ca beam and the staff of the target laboratory for providing high-quality targets. We acknowledge the technical support of J. Maurer, H. G. Burkhard, D. Racano, L. Braisz, D. Reemts, C. Droese, B. Schausten and I. Kostyuk. We thank P. Thirolf for his suggestions and comments. This work was supported by the German Federal Ministry of Education and Research under contracts 06MZ169I, 06LM236I, FAIR NuSTAR 05P09RDFN4, 05P12RDFN8 and 05P15RDFN1; by the GSI; and by the Helmholtz-Institut Mainz.

Author information




W.L., H.B., M.B., T.W., P.v.D., C.E.D., M.H. and A.Y. provided experimental equipment. M.L., F.L., P.C., S.R., W.L., P.K., M.B., F.P.H., D.A., C.W., A.K.M., B.C., R.F., F.G., O.K., J.K., J.E., S.G. and E.M.R. performed the experiments. F.L., P.C., H.B., S.R. and M.L. analysed the data. M.L. wrote the manuscript with input from all authors.

Corresponding author

Correspondence to Mustapha Laatiaoui.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information

Nature thanks V. Fedosseev and L. Visscher for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 Principle of the RADRIS technique.

Laser spectroscopy on radionuclides (spheres) after their production and transmission through the velocity filter SHIP22. a, Thermalization of the fusion products in the buffer gas; b, accumulation on the catcher filament; c, re-evaporation from the filament; d, two-step photoionization of neutral atoms; e, accumulation of re-ionized fusion products on the PIPS detector; f, decay detection.

Extended Data Table 1 Uncertainties on the value of the 254No first-step resonance

Related audio

PowerPoint slides

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Laatiaoui, M., Lauth, W., Backe, H. et al. Atom-at-a-time laser resonance ionization spectroscopy of nobelium. Nature 538, 495–498 (2016).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links