Laser Excitation of the Th-229 Nucleus.

The 8.4 eV nuclear isomer state in Th-229 is resonantly excited in Th-doped CaF_{2} crystals using a tabletop tunable laser system. A resonance fluorescence signal is observed in two crystals with different Th-229 dopant concentrations, while it is absent in a control experiment using Th-232.

946-nm Nd:YAG digital-locked laser at 1.1 × 10 in 1 s and transfer-locked to a cryogenic silicon cavity.

We present a Nd:YAG ultra-stable laser system operating at 946 nm and demonstrate a fractional frequency instability of 1.1×10 at 1 s by pre-stabilizing it to a 30-cm-long ULE cavity at room temperature. All key analog components have been replaced by FPGA-based digital electronics.

Nuclear Charge Radii of ^{229}Th from Isotope and Isomer Shifts.

The isotope ^{229}Th is unique in that it possesses an isomeric state of only a few electron volts above the ground state, suitable for nuclear laser excitation. An optical clock based on this transition is expected to be a very sensitive probe for variations of fundamental constants, but the nuclear properties of both states have to be determined precisely to derive the actual sensitivity. We carry out isotope shift calculations in Th^{+} and Th^{2+} including the specific mass shift, using a combination of configuration interaction and all-order linearized coupled-cluster methods and estimate the uncertainty of this approach.

Laser spectroscopic characterization of the nuclear-clock isomer Th.

The isotope Th is the only nucleus known to possess an excited state Th in the energy range of a few electronvolts-a transition energy typical for electrons in the valence shell of atoms, but about four orders of magnitude lower than typical nuclear excitation energies. Of the many applications that have been proposed for this nuclear system, which is accessible by optical methods, the most promising is a highly precise nuclear clock that outperforms existing atomic timekeepers. Here we present the laser spectroscopic investigation of the hyperfine structure of the doubly charged Th ion and the determination of the fundamental nuclear properties of the isomer, namely, its magnetic dipole and electric quadrupole moments, as well as its nuclear charge radius.

Generalized Ramsey excitation scheme with suppressed light shift.

We experimentally investigate a recently proposed optical excitation scheme V. I. Yudin et al.