Related papers: Limit on the Temporal Variation of the Fine-Struct…
A new experiment to test for the time independence of the fine structure constant, alpha, is proposed. The experiment utilizes orthogonally polarized Transverse Electric and Transverse Magnetic Whispering Gallery Modes in a single sapphire…
We have measured the 1S - 2S transition frequency in atomic hydrogen via two photon spectroscopy on a 5.8 K atomic beam. We obtain $f_{1S-2S} = 2 466 061 413 187 035 (10)$ Hz for the hyperfine centroid. This is a fractional frequency…
We perform accurate calculations of the dependence of transition frequencies in two valence electron atoms and ions on a variation of the fine structure constant, alpha. The relativistic Hartree-Fock method is used with many-body…
The $^1\mathrm{S}_0$-$^3\mathrm{P}_0$ clock transition frequency $\nu_\text{Sr}$ in neutral $^{87}$Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years.…
Accurate and comprehensive atomic data are essential for the modelling of stellar spectra. Uncertainties in the oscillator strengths of specific lines used for abundance analyses directly translate into uncertainties in the derived…
We calculate the dependence of atomic transition frequencies on the fine structure constant, $\alpha = e^2/\hbar c$, for some ions of Ti, Mn, Na, C, and O. The results of these calculations will be used in the search for variation of alpha…
We study transitions between ground and low-energy excited states of heavy ions corresponding to s-d single-electron transitions or s^2-d^2 double-electron transitions. The large nuclear charge Z and significant change in angular momentum…
We consider a narrow magneto-dipole transition in the $^{169}$Tm atom at the wavelength of $1.14\,\mu$m as a candidate for a 2D optical lattice clock. Calculating dynamic polarizabilities of the two clock levels $[\text{Xe}]4f^{13}6s^2…
Atom interferometers with long baselines are envisioned to complement the ongoing search for dark matter. They rely on atomic manipulation based on internal (clock) transitions or state-preserving atomic diffraction. Principally, dark…
An electronically variational approach to the calculation of atomic hyperfine structure transition energies under the influence of static external electric fields is presented. The method avoids the calculation of intermediate atomic states…
Microwave and submillimeter molecular transition frequencies between nearly degenerated rotational levels, tunneling transitions, and mixed tunneling-rotational transitions show an extremely high sensitivity to the values of the…
The frequency ratio of the 1S0(F=1/2)-3P0(F=1/2) clock transition in 171Yb and the 1S0(F=9/2)-3P0(F=9/2) clock transition in 87Sr is measured by an optical-optical direct frequency link between two optical lattice clocks. We determined the…
We report on a frequency measurement of the $(3s^2)^1S_0\to(3s3p)^3P_1$ clock transition of $^{24}$Mg on a thermal atomic beam. The intercombination transition has been referenced to a portable primary Cs frequency standard with the help of…
We used a Cs atomic fountain frequency standard to measure the Stark shift on the ground state hyperfine transiton frequency in cesium (9.2 GHz) due to the electric field generated by the blackbody radiation. The measures relative shift at…
High-precision spectroscopy of simple atomic systems can be used to advance the theory of atomic energy levels but can also serve as a sensitive probe of nuclear charge radii. For this last purpose, we report an improved measurement of the…
We calculated the dependence of the transition frequencies on the fine-structure constant $\alpha$ ($q$-factors) for Ni~II. Nickel is one of the few elements with high sensitivity to $\alpha$-variation, whose lines are observed at high…
Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variation of physical ``constants'' in the Universe. Detection of high-redshift absorption systems intersecting the sight lines towards distant…
The differential polarizability, due to near-infrared light at 1126 nm, of the 27Al+ 1S0 -> 3P0 clock transition is measured to be 4\pi\epsilon_0 x (1.6 +/- 0.5) x 10^{-31} m^3. This measurement is combined with experimental oscillator…
Transition frequencies of Fe II ion are known to be very sensitive to variation of the fine structure constant \alpha. The resonance absorption lines of Fe II from objects at cosmological distances are used in a search for the possible…
A full evaluation of the uncertainty budget for the ytterbium ion optical clock at the National Physical Laboratory (NPL) was performed on the electric octupole (E3) $^2\mathrm{S}_{1/2}\,\rightarrow\, ^2\mathrm{F}_{7/2}$ transition. The…