We present a rigorous derivation of the nuclear spin-rotation and spin-torsion coupling terms in the hyperfine Hamiltonian for molecules with internal rotation. Our formulas differ from the expressions derived by Heuvel and Dymanus [J. Mol. Spectrosc. 47, 363 (1973)], which these authors used and which were also applied recently by others to interpret experimental hyperfine spectra of such mole...

We calculate three-loop radiative-recoil corrections to hyperfine splitting in muonium generated by the diagrams with the first order electron and muon polarization loop insertions in graphs with two exchanged photons. These corrections are enhanced by the large logarithm of the electron-muon mass ratio. The leading logarithm squared contribution was obtained a long time ago. Here we calculate ...

A dense grid of reference lines in the hyperfine structure of the B-X transitions of molecular iodine ((127)I(2)) is presented. Frequencies of 481 "t"-hyperfine components in 15 vibrational bands covering the wavelength range 595-655 nm were determined with an absolute accuracy of 1.0 MHz (1varsigma uncertainty). Spectra were obtained by Doppler-free saturation spectroscopy using a cw ring-dye ...

The lowest energy rotational transitions of CD and CH in their 2 r ground electronic states have been directly measured using submillimeter direct absorption spectroscopy. These two radicals were produced in an electrical discharge of either CD4 (or CH4 and D2) or CH4. The J 1⁄4 3/2 1/2, N 1⁄4 1 1 transition at 439 GHz and the J 1⁄4 3/2 3/2 and 5/2 3/2 fine structure lines of theN 1⁄4 2 1 rotat...

The hyperfine-induced 2s2p P0−2s 2 S0 transition rate for Be-like 47Ti18+ was recently measured in a storage-ring experiment by Schippers et al. [Phys. Rev. Lett. 98, 033001 (2007)]. The measured value of 0.56(3) s−1 is almost 60% larger than the theoretical value of 0.356 s−1 from a multiconfiguration Dirac-Fock calculation by Marques et al. [Phys. Rev. A 47, 929 (1993)]. In this work, we use ...

Hyperfine quantum-beat spectroscopy has been utilized in a pump-probe configuration to measure magnetic dipole (A) and electric quadrupole (B) coupling constants in the 3d D3/2 and 3d D5/2 levels of three isotopes of potassium. For many of these levels, the largest hyperfine splitting is smaller than the natural width, and so a subnatural linewidth technique is required. In the experiments, the...

Hyperfine splittings between the heavy vector (D∗, B∗) and pseudoscalar (D, B) mesons have been calculated numerically in lattice QCD, where the pion mass (which is related to the light quark mass) is much larger than its physical value. Naive linear chiral extrapolations of the lattice data to the physical mass of the pion lead to hyperfine splittings which are smaller than experimental data. ...

The Ir-Fe and Ir-Ni alloy systems were studied over the whole composition range by means of the nuclear resonance absorption of the 73 keV y-rays of 193Jr and of the 14.4 keV y-rays of 57Fe. The magnetic hyperfine field at the Ir-nuclei in Ir-Ni alloys decreases approximately linearly with the Ir concentration from — 460 kOe at 4.2 K in very dilute alloys to zero at about 20 at.-% Ir. This beha...

The CeMIn5 heavy fermion compounds have attracted enormous interest since their discovery six years ago. These materials exhibit a rich spectrum of unusual correlated electron behavior, and may be an ideal model for the high temperature superconductors. As many of these systems are either antiferromagnets, or lie close to an antiferromagnetic phase boundary, it is crucial to understand the beha...

Two-photon transitions between atomic states of total electronic angular momentum Ja = 0 and Jb = 1 are forbidden when the photons are of the same energy. This selection rule is analogous to the Landau-Yang theorem in particle physics that forbids decays of vector particle into two photons. It arises because it is impossible to construct a total angular momentum J2γ = 1 quantum-mechanical state...