Identification of hyperfine structure components of the iodine molecule at 640 nm wavelength

The frequencies and the relative intensities of rotation-vibration transitions of ¹²⁷I₂, ¹²⁹I₂ and ¹²⁷I¹²⁹I near the HeNe laser emission wavelength of 640 nm have been calculated. Interpolation formulas for the differences of the electric quadrupole constants ΔeQq and of the spin-rotation constants ΔC of ¹²⁷I₂ are given. Most of the weak saturated-aborption lines, elsewhere published, have been identified as cross-over and forbidden lines of the transitions P(10)8-5 and R(16)8-5.     

Measurements and analysis of collisional line-mixing within nuclear hyperfine components of helium broadened HI lines

The absorption by the R (0) and R (1) lines of the fundamental band of HI broadened by He have been measured in the 0-500 mbar pressure range using a tunable difference frequency generation laser spectrometer. The observed transmissions have been fitted and analyzed with a line-coupling model based on the infinite order sudden approximation. It is demonstrated that the three hyperfine components of the R (0) manifold have identical widths and are not coupled by collisions. On the contrary, the profile of the R (1) manifold cannot be modeled without accounting for both line-mixing and for the fact that the nine hyperfine components have different broadening parameters. This is, to our knowledge, the first demonstration of line coupling within hyperfine components.     

Determination of hyperfine interactions from partly resolved moessbauer spectra

Moessbauer spectra with different sets of parameters were calculated. A fit with a superposition of Lorentzians to these theoretical spectra showed, that systematic errors must be expected if the hyperfine structure of the spectrum is only partly resolved. Correction factors for some simple cases are given. Experiments to test the calculations were performed with¹³³Cs (81 keV transition),¹⁶⁵Ho (94.7 keV transition) and¹⁷⁸Hf (93 keV transition). In all cases fits using the transmission integral and superpositions of Lorentzians showed the expected trends. We get the following results: $$\begin{gathered} ^{133} Cs:\frac{{g_{ex} }}{{g_{gr} }} = 1.90\left( 4 \right) \hfill \\ ^{165} Ho:\tau \left( {94.7keVlevel} \right) = 32\left( 1 \right)ps \hfill \\ \frac{{g_{ex} }}{{g_{gr} }} = 0.77\left( 3 \right) \hfill \\ ^{178} Hf:|H_{eff} \left( {4K,in iron} \right)| = 633\left( {40} \right)KG \hfill \\ |H_{eff} \left( {77K,in iron} \right)| = 630\left( {41} \right)KG. \hfill \\ \end{gathered}$$      

Intensities of hyperfine components in saturation spectroscopy

A theory is presented for the intensities of hyperfine components in saturation spectroscopy. We use a diagrammatic approach to nonlinear processes to derive closed-form formulas for the intensities of recoil doublets and of Doppler-generated level crossings. We discuss the influence of the terms introduced by hyperfine coherences in saturation spectroscopy. We also demonstrate spectroscopic stability when the hyperfine splittings are negligible. A catalog of simple formulas is given in view of applications to current spectroscopy and is illustrated by recent examples, including Doppler-free polarization spectroscopy. The extension to other sub-Doppler techniques such as two-photon Doppler-free spectroscopy is outlined.     

Asymmetry in the nuclear magnetic shielding tensor

The applicability of Green's function (GF) and Feynman path-integral quantum Monte Carlo (QMC) methods for the simulation of cyclic networks with (4n + 2) and 4n (n = 1, 2, 3, …) electrons is analysed. Both QMC techniques are employed in simulations on the basis of the simple Hückel Hamiltonian which is exclusively defined by nearest-neighbour hopping elements. In addition we have used the Pariser-Parr-Pople (PPP) Hamiltonian to perform GF QMC simulations. The electronic energies E derived by the QMC methods are compared either with Hückel molecular orbital (HMO) results or exact configuration interaction data where (π) electronic correlations are fully taken into account. A sign problem occurs in QMC simulations of 4n annulenes. This leads to an error in the total energy in the standard formulations of the employed QMC techniques, which is enhanced with decreasing ring size. A simple modification in the QMC formalisms is suggested to avoid the numerical uncertainties caused by the sign problem in 4n annulenes. Renormalization of the kinetic hopping integrals t by t cos (π/M) with M abbreviating the number of atomic sites leads to ground state energies as well as any other quantity close to the values derived by conventional diagonalization techniques. Substitution of t against t cos (π/M) conserves a common sign of all matrix elements containing the hopping. The occurrence of negative probabilities, which lead to numerical problems in the QMC simulations, is thereby prevented. The transformation suggested in 4n rings has a formal connection to so-called Möbius rings.     

The dielectric tensor components of anthracene derived from energy loss experiments

Energy loss spectra of anthracene single crystals corresponding to the dielectric tensor elements ? _xx , ? _yy and ? _zz were measured with 60 keV electrons, after having fixed the main axes of the dielectric tensor corresponding to ? _xx and ? _zz . The real and imaginary parts of the dielectric tensor elements are derived from the loss functions by a Kramers-Kronig-analysis. The results are compared with those obtained by other autors and with measurements on graphite.     

External reflection from dielectrics at microwave frequencies

3 cm microwave are being used to investigate the beam shifts which occur for external reflection from a planar dielectric interface. The adaptation of a planar wave theory to the microwave case has proved successful in predicting the magnitudes and direction of such shifts.     

Coherent control of two nuclear spins using the anisotropic hyperfine interaction

We demonstrate coherent control of two nuclear spins mediated by the magnetic resonance of a hyperfine-coupled electron spin. This control is used to create a double-nuclear coherence in one of the two electron spin manifolds, starting from an initial thermal state, in direct analogy to the creation of an entangled (Bell) state from an initially pure unentangled state. We identify challenges and potential solutions to obtaining experimental gate fidelities useful for quantum information processing in this type of system.     

Determination of hyperfine parameters using quantum beats

We have observed the delayed time spectra of the coherently scattered radiation following nuclear Bragg diffraction of incident synchrotron radiation pulses. The measurements were carried out using single crystals of⁵⁷Fe-YIG and⁵⁷FeBO₃ by conventional coincidence techniques. Although the intention of these measurements was only to show effects like speed-up and quantum beats, the spectra also provide the possibility of a sensitive direct measure of the hyperfine interaction parameters. It is demonstrated that even with a counting rate of only 1 Hz it was possible to obtain within 1–2 hours (in the case of⁵⁷FeBO₃) spectra of sufficient statistics to derive precise hyperfine parameters.     

Evolution of nuclear shells due to the tensor force

The monopole effect of the tensor force is presented, exhibiting how spherical single-particle energies are shifted as protons or neutrons occupy certain orbits. An analytic relation for such shifts is shown, and their general features are explained intuitively. Single-particle levels are shown to change in a systematic and robust way, by using the pi + rho meson exchange tensor potential, consistently with the chiral perturbation idea. Several examples are compared with experiments.     

Relativistic interpretation of the nature of the nuclear tensor force

The spin-dependent nature of the nuclear tensor force is studied in detail within the relativistic HartreeFock approach. The relativistic formalism for the tensor force is supplemented with an additional Lorentz-invariant tensor formalism in the a-scalar channel, so as to take into account almost fully the nature of the tensor force brought about by the Fock diagrams in realistic nuclei. Specifically, the tensor sum rules are tested for the spin and pseudospin partners with and without nodes, to further understand the nature of the tensor force within the relativistic model. It is shown that the interference between the two components of nucleon spinors causes distinct violations of the tensor sum rules in realistic nuclei, mainly due to the opposite signs on the κ quantities of the upper and lower components, as well as the nodal difference. However, the sum rules can be precisely reproduced if the same radial wave functions are taken for the spin/pseudo-spin partners in addition to neglecting the lower/upper components,revealing clearly the nature of the tensor force.     

A new parametrization method for hyperfine interactions. Determination of nuclear quadrupole moments almost free of Sternheimer corrections

A method of simultaneous parametrization of one- and two-body interactions in atomic hyperfine structure (HFS) of the configurations (3d+4s)^N+2 is proposed. It is shown that the HFS of these configurations can be parametrized by the use of sixteen adjustable radial parameters for the magnetic dipole interaction and twelve radial parameters for the electric quadrupole interaction. From these one- and two-body parameters nuclear quadrupole moments can be evaluated which are almost free of Sternheimer corrections.     

Hartree-Fock and density functional complete basis-set (CBS) predicted nuclear shielding anisotropy and shielding tensor components

The nuclear shielding anisotropy and shielding tensor components calculated using the hybrid density functional B3PW91 are reported for a model set of compounds comprised of N2, NH3, CH4, C2H4, HCN and CH3CN. An estimation of density functional theory (DFT) and Hartree-Fock complete basis-set limit (CBS) parameters from a 2 (3) point exact fit vs. least-squares fit was obtained with the cc-pVxZ and aug-cc-pVxZ basis sets (x=D, T, Q, 5, 6). Both Hartree-Fock- and DFT-predicted CBS shielding anisotropies and shielding tensor components of the model molecules were in reasonable agreement with available experimental data. The utility of using a limited CBS approach for calculating accurate anisotropic shielding parameters of larger molecules as complementary methods to solid-state NMR is proposed.