Related papers: First observation of two hyperfine transitions in …
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…
We present the detection of the highly forbidden $2^{3\!}S_1 \rightarrow 3^{3\!}S_1$ atomic transition in helium, the weakest transition observed in any neutral atom. Our measurements of the transition frequency, upper state lifetime, and…
The hyperfine structure of the ground state of erbium doped yttrium orthosilicate is analyzed with the use of electron paramagnetic resonance experiments in a tunable microwave resonator. This work was prompted by the disagreement between…
Theoretical investigations of the hyperfine structure of the hydrogen molecular ion (one electron and two protons) are discussed. The nuclear spin-rotation interaction has been found to be of the same sign as in the hydrogen molecule and…
We search for three-neutron resonances which were predicted from pion double charge exchange experiments on He-3. All partial waves up to J=5/2 are nonresonant except the J=3/2^+ one, where we find a state at E=14 MeV energy with 13 MeV…
We have measured twelve transition frequencies of the antiprotonic helium atom (pbar-He+) with precisions of 0.1--0.2 ppm using a laser spectroscopic method. The agreement between the experiment and theories was so good that we can put a…
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…
This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that…
Recently we reported a high precision optical frequency measurement of the (v,L):(0,2)->(8,3) vibrational overtone transition in trapped deuterated molecular hydrogen (HD+) ions at 10 mK temperature. Achieving a resolution of 0.85…
The [$^{12}$C II] emission at 158 $\mu$m is a key cooling line of the interstellar medium and traces gas kinematics in spectrally resolved observations. Its spectral profile is often modified by optical depth effects. The intrinsic line…
We report the first direct measurement of the hyperfine transition of the ground state positronium. The hyperfine structure between ortho-positronium and para-positronium is about 203 GHz. We develop a new optical system to accumulate about…
A measurement of the double-spin asymmetry from electron-$^{3}$He scattering in the threshold region of two- and three-body breakup of $^{3}$He was performed at Jefferson Lab, for Q$^{2}$ values of 0.1 and 0.2 (GeV/$c$)$^{2}$. The results…
Hyperfine intervals in light hydrogenic atoms and ions are among the most accurately measured quantities in physics. The theory of QED corrections has recently advanced to the point that uncalculated terms for hydrogenic atoms and ions are…
We have measured transition frequencies, isotope shifts and hyperfine structure splittings in the $3 d^{2}\left({ }^{3\!}F\right) 4 s\,{ }^{4} F_J\rightarrow 3 d^{2}\left({ }^{3\!} F\right) 4 p \,^{4} G_{J+1}$ transitions in Ti$^+$ ions for…
We have observed the rotational ground-state (J = 1-0) transitions of DCO+, HN13C and DNC with the IRAM 30m telescope toward the dark cloud LDN 1512 which has exceptionally narrow lines permitting hyperfine splitting to be resolved in part.…
We have measured hyperfine structure in the first-excited $P$ state ($D$ lines) of all the naturally-occurring alkali atoms. We use high-resolution laser spectroscopy to resolve hyperfine transitions, and measure intervals by locking the…
The off-diagonal hyperfine interaction between the 6p1/2 and 6p3/2 states in 133Cs is evaluated in third-order MBPT giving 37.3 Hz and 48.3 Hz, respectively, for second-order energies of the 6p3/2 F=3 and F=4 levels. This result is a factor…
We investigate the microwave spectra of ultracold alkali metal dimers in magnetic, electric and combined fields, taking account of the hyperfine structure due to the nuclear spins. We consider the molecules 41K87Rb and 7Li133Cs, which are…
Precision spectroscopy of simple atomic systems has refined our understanding of the fundamental laws of quantum physics. In particular, helium spectroscopy has played a crucial role in describing two-electron interactions, determining the…
Jefferson Lab experiment E01-012 measured the He-3 spin-structure functions and virtual photon asymmetries in the resonance region in the momentum transfer range 1.0<Q**2<4.0(GeV/c)**2. Our data, when compared with existing deep inelastic…