Related papers: Improved theory of helium fine structure
We present recent progress in the calculation of the helium fine-structure splitting of the 2^3P_J states, based on the quantum electrodynamic theory. Apart from the complete evaluation of m\alpha^7 and m^2/M\alpha^6 corrections, we have…
In order to explain discrepancies between theoretical predictions and experimental data for the helium fine structure, we check and recalculate all theoretical contributions up to orders m\alpha^7 and m^2/M\alpha^6. The previous result for…
Calculational results are presented for the fine-structure splitting of the 2^3P state of helium and helium-like ions with the nuclear charge Z up to 10. Theoretical predictions are in agreement with the latest experimental results for the…
Increasing accuracy of the theory and experiment of the $n$$=$$2$ $^3$P fine structure of helium has allowed for increasingly-precise tests of quantum electrodynamics (QED), determinations of the fine-structure constant $\alpha$, and…
We critically examine the current status of theoretical calculations of the energies, the fine structure, and the isotope shift of the lowest-lying states of helium, searching for unresolved discrepancies with experiments. Calculations are…
We report a calculation of the fine structure splitting in light helium-like atoms, which accounts for all quantum electrodynamical effects up to order \alpha^5 Ry. For the helium atom, we resolve the previously reported disagreement…
Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electro-optic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new…
Transition frequencies and fine-structure splittings of the $2\,{}^3\!S_1 \rightarrow 2\,{}^3\!P_{\!J}$ transitions in helium-like $^{12}\mathrm{C}^{4+}$ were measured by collinear laser spectroscopy on a 1-ppb level. Accuracy is increased…
For decades, improved theory and experiment of the $n=2$ $^3$P fine structure of helium have allowed for increasingly-precise tests of quantum electrodynamics, determinations of the fine-structure constant $\alpha$, and limitations on…
There is presently disagreement between theory and experiment as well as between different theoretical calculations concerning the fine-structure splitting of the lowest P state of the neutral helium atom. We believe that we have found a…
In this work we describe the latest results for the measurements of the hyperfine structure of antiprotonic helium-3. Two out of four measurable super-super-hyperfine SSHF transition lines of the (n,L)=(36,34) state of antiprotonic helium-3…
We present a calculation of the hyperfine splitting of the $2^3S$ state in the $^3$He atom with inclusion of all QED effects up to $\alpha^3E_F$, where $E_F$ is the Fermi splitting. Using the experimental value of the $1S$ hyperfine…
QED theory of the hyperfine splitting of the $1s$ and $2s$ state in hydrogen isotopes and helium-3 ion is considered. We develop an accurate theory of a specific difference 8E_{HFS}(2s)-E_{HFS}(1s). We take into account fourth order…
Despite quantum electrodynamics (QED) being one of the most stringently tested theories underpinning modern physics, recent precision atomic spectroscopy measurements have uncovered several small discrepancies between experiment and theory.…
The $1\mathrm{s}n\mathrm{p}\,^3\mathrm{P}_J$ fine structure of high Rydberg states in helium has been measured by microwave spectroscopy of single-photon transitions from $1\mathrm{s}n\mathrm{s}\,^3\mathrm{S}_1$ levels in pulsed supersonic…
Corrections of order $\alpha^4$Ry are calculated for the singlet states $1^1S_0$ and $2^1S_0$ of the helium atom. The result for $1^1S_0$ state is in slight disagreement with that of Korobov and Yelkhovsky in [Phys. Rev. Lett. {\bf 87},…
We report on a theoretical calculation and a new experimental determination of the 1s3p ^3P_J fine structure intervals in atomic ^4He. The values from the theoretical calculation of 8113.730(6) MHz and 658.801(6) MHz for the nu_{01} and…
Post-selecting output states in measurements can effectively amplify weak signals and improve precision. However, post-selection effects may also introduce unintended biases in precision measurements. Here, we investigate the influence of…
It is shown that the fine structure splittings of the $2 ^3P_J$ and $3 ^3P_J$ excited states in charmonium are as large as those of the $1^3P_J$ state if the same $\alpha_s(\mu)\approx 0.36$ is used. The predicted mass $M(2 ^3P_0)=3.84$ GeV…
We report on the first experimental results for microwave spectroscopy of the hyperfine structure of antiprotonic He-3. Due to the helium nuclear spin, antiprotonic He-3 has a more complex hyperfine structure than antiprotonic He-4 which…