Comparative studies of the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of 25Mg+

We have employed the relativistic coupled cluster theory to calculate the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of singly ionized magnesium. Comparison with experimental and the other theoretical results are done and predictions are also made for a few low lying excited states which could be of interest. We have made comparative studies of the important many body effects contributing to the hyperfine constants for the different states of the ion.     

Hyperfine quenching of polarized two-electron ions in an external magnetic field

The hyperfine quenching mechanism of metastable states in polarized heliumlike heavy ions is considered. The lifetime dependence of these states on the ion polarization in an external magnetic field is established. This dependence is presented for the ²³P₀ state of the europium (Z=63) ion and is proposed as a method for the measurement of the ion polarization in experiments for the search of parity violating effects.     

Manipulation of individual hyperfine states in cold trapped molecular ions and application to HD+ frequency metrology

Advanced techniques for manipulation of internal states, standard in atomic physics, are demonstrated for a charged molecular species for the first time. We address individual hyperfine states of rovibrational levels of a diatomic ion by optical excitation of individual hyperfine transitions, and achieve controlled transfer of population into a selected hyperfine state. We use molecular hydrogen ions (HD+) as a model system and employ a novel frequency-comb-based, continuous-wave 5 μm laser spectrometer. The achieved spectral resolution is the highest obtained so far in the optical domain on a molecular ion species. As a consequence, we are also able to perform the most precise test yet of the ab initio theory of a molecule.     

Laser assisted decay spectroscopy at the CRIS beam line at ISOLDE

The new collinear resonant ionization spectroscopy (Cris) experiment at Isolde, Cern uses laser radiation to stepwise excite and ionize an atomic beam for the purpose of ultra-sensitive detection of rare isotopes and hyperfine structure measurements. The technique also offers the ability to purify an ion beam that is contaminated with radioactive isobars, including the ground state of an isotope from its isomer. A new program using the Cris technique to select only nuclear isomeric states for decay spectroscopy commenced last year. The isomeric ion beam is selected using a resonance within its hyperfine structure and subsequently deflected to a decay spectroscopy station. This consists of a rotating wheel implantation system for alpha and beta decay spectroscopy, and up to three high purity germanium detectors for gamma-ray detection. This paper gives an introduction to the Cris technique, the current status of the laser assisted decay spectroscopy set-up and recent results from the experiment in November 2011.     

Laser spectroscopy of the 1s HFS of H-like ions at a bunched beam in the storage ring ESR

The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in ²⁰⁷Pb⁸¹⁺. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics from an ion beam at relativistic velocities. This revised version was published online in July 2006 with corrections to the Cover Date.     

Velocity-selective spectroscopy measurements of Rydberg fine structure states in a hot vapor cell

A velocity-selective spectroscopy technique for studying the spectra of Rydberg gases is presented. This method provides high-resolution spectrum measurements. We present experimental results for a ladder system 6S_(1/2)→ 6P_(3/2)→ nS(D)electromagnetically-induced transparency involving highly-excited Rydberg states. Based on a radio-frequency modulation technique, we measure the hyperfine structure splitting of intermediate states and the fine structure splitting of Rydberg states in a room temperature ~(133)Cs vapor cell. The experimental data and theoretical predictions show excellent agreement.     

Hyperfine structure and lifetimes of metastable states studied by means of laser excitation of stored ions

Studies of hyperfine structure of metastable states are facilitated by storage rings and ion traps. Here we report on the development of a method to study metastable states of stored singly charged ions by laser excitation. The experiments were performed at the accelerator and storage ring CRYRING at the Manne Siegbahn Laboratory in Stockholm. We discuss means to improve the resolution and the possibility to extend the method to highly charged ions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relativistic coupled cluster method

Relativistic coupled cluster method (CCM) is applied to compute the low lying excited and ion states of strontium and ytterbium atom. The resulting excitation and ionization energies are in excellent agreement with experimental data and with other correlated calculations. The nuclear magnetic dipole hyperfine constants (A) and electric quadrupole hyperfine constants (B) of excited states are also evaluated and are in accord with experiment. We further address the basis set dependency of the computed properties.     

Polarized nuclei from unpolarized atoms two-photon resonantly ionized via hyperfine structure energy levels

Nuclear spin polarization of the residual ion formed from an alkali atom after its resonant two-photon two-light beam ionization via hyperfine structure energy states is calculated in second-order time-dependent perturbation approach for atom-light interaction and taking into account all photoionization channels permitted in the electric-dipole approximation.     

Transient hyperfine magnetic fields

Fast ions traversing magnetized materials experience very large transient hyperfine magnetic fields. The processes responsible for these interactions are related to the interchange of electrons between the moving ion and the polarized medium. The dependence of the transient hyperfine fields on the atomic number and the velocity of the ion, and on the magnetization of the host has been mapped for a wide range of nuclei and magnetic hosts. The experimental evidence supporting specific models will be presented and applications to the measurement of magnetic moments of short-lived excited states will be described. Supported in part by the National Science Foundation     

Extraction of hyperfine anomalies without precise values of the nuclear magnetic dipole moment

A new method for extracting the hyperfine anomaly from experimental hyperfine structure constants is suggested. Instead of independent high-precision measurements of the nuclear magnetic dipole moment, precise measurements of magnetic dipole hyperfine interaction constants for two atomic states and a theoretical analysis can be used. This can lead to determination of hyperfine anomaly for radioactive isotopes where the nuclear magnetic dipole moment is not known with high accuracy. Received: 17 February 1998     

The understanding of nuclear structure through Mössbauer experiments

Mössbauer's discovery vitalized the study of hyperfine interactions on nuclear states. The technique has been used to measure the electromagnetic moments of scores of nuclear levels and the results, especially on rotational states, have been important to our understanding of nuclear structure. Equally signicant for nuclear physics has been the deep insight which Mössbauer studies have given us of the hyperfine interaction itself; using that knowledge, and a variety of techniques, the measurements of nuclear magnetic moments are now reliable and routine.     

Hyperfine structure and isotope shift of high-lying metastable states of rhenium

Fourteen transitions in ReI, starting from high-lying metastable states belonging to the configurations (5d+6s)⁷, have been studied by laser-induced fluorescence in a collimated atomic beam, and accurate values for the isotope shifts in these transitions as well as for the hyperfine structure constants of 13 metastable and 9 excited states have been obtained. In addition, high precision measurements of the hyperfine structure of the states 5d ⁵ 6s ^{2 4} D _7/2 and 5d ⁶ 6s ⁶ D _{1/2, 3/2, 5/2, 9/2} have been performed using the atomic beam magnetic resonance technique coupled with laser-induced state-selective detection of metastable atoms. The analysis of the hyperfine structure data yields experimental evidence for far configuration mixing effects on the off-diagonal spin-dipole matrix elements. The phenomenological interpretation of the isotope shifts shows the significance of off-diagonal field-shift effects.     

Hyperfine Constants for Low-Lying States in ^137Ba^＋

Relativistic many-body perturbation calculation is applied to calculate the hyperfine constants for the lowlying states 6S1/2, 6P1/2, 6P3/2, 5D3/2, and 5D5/2 in the alkaline earth ion ^137Ba^＋. The zeroth-order hyperfine constants are calculated with Dirac-Fock wave functions, and the finite basis sets of the Dirac-Fock equation are constructed by B splines. With the finite basis sets, the core polarization and the correlation effect are calculated. The final results for magnetic dipole hyperfine a constants are obtained.     

Lifetime measurements of metastable states in CRYRING

Collinear ion beam laser spectroscopy has been utilized in the ion storage ring CRYRING in order to measure lifetimes of metastable states in singly charged ions. The laser light has been used for selective probing of the population decay of individual fine structure or hyperfine structure states. With the use of a mechanical shutter, time resolved studies could be performed with millisecond resolution. In another experiment, the cw laser light was used to optically pump stored ions from the ground state into a specific metastable state. With most of the stored ions in the metastable state, direct observation of the decay of the forbidden transition from the metastable state to the ground state could be observed passively. Measurements of metastable lifetimes in Ca⁺, Sr⁺, Xe⁺ and Eu⁺ will be discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

A molecular beam laser-microwave double-resonance spectrometer for precise measurements of high temperature molecules

A laser-microwave double-resonance experiment has been developped basing on the principle of the known laser-rf double-resonance technique. This novel beam experiment allows high-resolution measurements of rotational transitions in a molecular ground state. The method was applied to the high-temperature radical CaCl to study the hyperfine structure of transitions between low-lying rotational states. Microwave scans yielded linewidths of 15–20 kHz limited only by time-of-flight broadening and residual Zeeman splitting.     

Fine structure and hyperfine structure of some excited states of helium

The fine structure and the hyperfine structure for some singly-excited and doubly-excited states of helium atom are calculated using Rayleigh-Ritz variational method with multi-configuration-interaction wave functions. The calculated results of the fine structure for the Rydberg series are in good agreement with other theoretical and experimental data. The hyperfine parameters and the hyperfine coupling constants of ³He are also obtained for this system.Received: 17 January 2003, Published online: 29 July 2003PACS: 32.10.Fn Fine and hyperfine structure - 31.30.Gs Hyperfine interactions and isotope effects, Jahn-Teller effect     

Atomic qubit manipulations with an electro-optic modulator

We report new techniques for driving high-fidelity stimulated Raman transitions in trapped-ion qubits. An electro-optic modulator induces sidebands on an optical source, and interference between the sidebands allows coherent Rabi transitions to be efficiently driven between hyperfine ground states separated by 14.53 GHz in a single trapped 111Cd+ ion.     

ESR study of exchange coupled pairs in copper diethyldithiocarbamate—explanation of the low temperature hyperfine anomaly

A study of the hyperfine interaction in the ESR of Cu-Cu pairs in single crystals of copper diethyldithiocarbamate as a function of temperature has shown distinct differences in the hyperfine structure in the two fine structure transitions at 20 K, the spectrum not having the same hyperfine intensity pattern in the low field fine structure transition in contrast to that of the high field transition. The details of the structure of both the fine structure transitions in the 20 K spectrum have now been explained by recognizing the fact that the mixing of the nuclear spin states caused by the anisotropic hyperfine interaction affects the electron spin states | + 1 > and | −> differently. This has incidentally led to a determination of the sign ofD confirming the earlier model. The anomalous hyperfine structure is found to become symmetric at 77 K and 300 K. It is proposed that the reason for this lies in the dynamics of spin-lattice interaction which limits the lifetime of the spin states in each of the electronic levels | − 1 >, | 0 > and | + 1 > The estimate of spin-lattice relaxation time agrees with those indicated from other studies. The model proposed here for the hyperfine interaction of pairs in the electronic triplet state is of general validity.     

Rubidium isotope shifts and hyperfine structure by two-photon spectroscopy with a multi-mode laser

The technique of two-photon laser spectroscopy without Doppler broadening is applied to atomic rubidium vapor. The hyperfine splitting and isotope shifts of several highly excited states are measured. We demonstrate the suitability of a tunable laser source oscillating simultaneously in many longitudinal modes for two-photon spectroscopy.