# Dysprosium experiments

The element of success

Atomic Dysprosium $(Z=66)$ has a ground-state configuration of $4f^{10} 6s^2$   and a total electronic angular momentum of $J=8$. Dysprosium is remarkable in that it contains a pair of nearly degenerate, opposite-parity levels, with $J=10$ which lie at an energy of $19798\, \text{cm}^{-1}$  above the ground state. In addition, Dy has seven stables isotopes at atomic masses of $A=156,\,158$ and $A=160-164$, whereas $\,^{161} Dy$ and $\,^{163} Dy$ have nonzero nuclear spin of $I=\frac{5}{2}$. The energy splitting between these states varies with isotope and ranges from a few MHz up to a few GHz.

Variation of fundamental constants

The pair of near-degenerate, opposite-parity states, is highly sensitive to variation of the fine-structure constant $\alpha$, due to large relativistic corrections of opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons which require optical frequency combs to compare energy levels in different atoms, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a radio-frequency (rf), electric-dipole transition between them. The precision spectroscopy of this energy difference over a period time (for example for a year) can be used to constrain both a temporal variation as well-as a gravitational-potential dependence of $\alpha$ since, during the data-acquisition period, the Earth is located at different values of the gravitational potential of the Sun.

Parity violation in atomic dysprosium

The high mass of dyspropsium and the small energy seperation between the opposite-parity states will lead to enhancement of weak mixing effects, making thus $Dy$ a promising system for the study of parity non-conservation. Furthermore, the availability of isotopes with nuclear spin allow for the possibility of measuring the anapole moment.

#### References

• N. Leefer, L. Bougas, D. Antypas, and D. Budker, Towards a new measurement of parity violation in dysprosium, arXiv:1412.1245
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• B. M. Roberts, Y. V. Stadnik, V. A. Dzuba, V. V. Flambaum, N. Leefer, and D. Budker, Limits on P-odd interactions of cosmic fields with electrons, protons and neutrons, Phys. Rev. Lett. 113, 081601 (2014); arXiv:1404.2723
• C.T.M. Weber, N. Leefer, and D. Budker, Investigation of ac-Stark shifts in excited states of dysprosium relevant to testing fundamental symmetries, Phys. Rev. A 88, 062503 (2013) (arXiv:1308.2391)
• Nathan Leefer and Michael A. Hohensee, An odd (parity) test of Lorentz symmetry with atomic dysprosium; (arXiv:1307.6762)
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• N. Leefer, C. T. M. Weber, A. Cingöz, J. R. Torgerson, D. Budker, New limits on variation of the fine-structure constant using atomic dysprosium; Phys. Rev. Lett. 111(6), 060801 (2013)  (arXiv:1304.6940); Raw Data[]
• N. Leefer, A. Cingöz, B. Gerber-Siff, Arijit Sharma, J. R. Torgerson, and D. Budker, Transverse laser cooling of a thermal atomic beam of dysprosium, Phys. Rev. A 81(4), 043427 (2010) (arXiv:0912.2133)
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• N. A. Leefer, A. Cingöz, D. Budker, S. J. Ferrell, V. V. Yashchuk, A. Lapierre, A.-T. Nguyen, S. K. Lamoreaux, J. R. Torgerson,  Variation of the Fine-Structure Constant and Laser Cooling of Atomic Dysprosium, in Proceedings of the 7th Symposium: Frequency Standards and Metrology, Asilomar, October 2008; Lute Maleki, Ed., World Scientific, pp. 34-43; arXiv:0811.3992
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