Optical clock based on two-photon spectroscopy of the nuclear transition in ion ${}^{229}$Th in a monochromatic field

Abstract

For the isotope ${}^{229}$Th we investigate the possibility of two-photon laser spectroscopy of the nuclear clock transition (148.38 nm) using intense monochromatic laser field at twice the wavelength (296.76 nm). Our estimates show that due to the electron bridge process in the doubly ionized ion ${}^{229}$Th${}^{2+}$ the sufficient intensity of a continuous laser field is about 10-100 kW/cm${}^2$, which is within the reach of modern laser systems. This unique possibility is an result of the presence in the electronic spectrum of the ion ${}^{229}$Th${}^{2+}$ of an exceptionally close intermediate (for the two-photon transition) energy level, forming a strong dipole ($E1$) transition with the ground state at the wavelength of 297.86 nm, which differs from the probe field wavelength (296.76 nm) by only 1.1 nm. The obtained results can be used for the practical creation of ultra-precise nuclear optical clocks based on thorium-229 ions. Moreover, we develop an alternative approach to the description of the electron bridge phenomenon in an isolated ion (atom) using the hyperfine interaction operator, that is important for the general quantum theory of an atom. In particular, this approach shows that the contribution to the electron bridge from the nuclear quadrupole moment can be comparable to the contribution from the nuclear magnetic moment.

8 pages, 2 figures

References in corpus (20)

• An atomic clock with $10^{-18}$ instability
• Single-Ion Atomic Clock with $3\times 10^{-18}$ Systematic Uncertainty
• A Single-Ion Nuclear Clock for Metrology at the 19th Decimal Place
• Highly charged ions: optical clocks and applications in fundamental physics
• Energy of the ${}^{229}$Th nuclear clock transition
• Frequency ratio of the ${}^{229\mathrm{m}}$Th nuclear isomeric transition and the ${}^{87}$Sr atomic clock
• Observation of the radiative decay of the ${}^{229}\mathrm{Th}$ nuclear clock isomer
• Hyper-Ramsey Spectroscopy of Optical Clock Transitions
• Measurement of the ${}^{229}$Th isomer energy with a magnetic micro-calorimeter
• Performance of a 229 Thorium solid-state nuclear clock
• A generalized Ramsey excitation scheme with suppressed light shift
• Auto-Balanced Ramsey Spectroscopy
• Energy of the ${}^{229}$Th Nuclear Clock Isomer Determined by Absolute $\gamma$-ray Energy Difference
• Generalized auto-balanced Ramsey spectroscopy of clock transitions
• Progress and perspectives on composite laser-pulses spectroscopy for high-accuracy optical clocks
• ${}^{229}{\mathrm{ThF}}_4$ thin films for solid-state nuclear clocks
• Modified hyper-Ramsey methods for the elimination of probe shifts in optical clocks
• Majority-Vote Model on a Random Lattice
• Excitation of the ${}^{229}$Th nucleus via a two-photon electronic transition
• Ultrastable optical, XUV and soft-x-ray clock transitions in open-shell highly charged ions