Diamagnetic Atoms Research Articles

Persistent Current of Dirac Sea: Application to Bismuth

Bismuth has been known to exhibit anomalously large diamagnetism which has been interpreted on the basis of the effective Hamiltonian of the Dirac type including spin-orbit coupling. Here the persistent current in a mesoscopic ring of bismuth is calculated. It is found that the magnetic flux induces persistent currents which have a spatial spread of the order of \(\xi =2\hbar v/E_{\rm G}\) ( v : velocity of the `Dirac' electron; E G : energy gap), just as in the atomic diamagnetism whose “atomic” size is gigantic and of mesoscopic scale.

Adiabatic-expansion method applied to diamagnetic Rydberg atoms.

We report on a successful implementation of the diabatic-by-sector method as applied to the computation of positive-energy diamagnetic Rydberg spectra of the alkali-metal atoms in a laboratory field (\ensuremath{\sim}6 T). The method provides the quantum-defect parameters directly, and opens up the possibility of accounting for various spectral features quantum mechanically.

Irregular wavefunction behavior in diamagnetic Rydberg hydrogen atoms: a dynamical SO (4, 2) group study

We extend the dymanical SO (4, 2) group to the study of the wavefunction behavior of diamagnetic Rydberg hydrogen atoms. The dynamical group allows a complete algebraization of the problem. When coupled with the use of the mini-max theorem, the procedure leads to an efficient algorithm for obtaining accurate eigenvalues and eigenvectors of arbitary highly excited states. Comparison of the classical and quantal behavior in both the regular and irregular regions is presented.

Diamagnetic Rydberg atom: Confrontation of calculated and observed spectra.

We present a detailed comparison of the observed and computed negative- and positive-energy spectrum of a Rydberg atom in a strong magnetic field. The study extends from -30 to +30 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ at a field of 6 T. The experimental resolution is sufficiently high to provide well-resolved spectra over the entire range. The spectrum calculated for hydrogen is in remarkable agreement with the spectrum observed in lithium.

Indo/Giao calculations of the NMR shielding constant including d orbitals

Application of the INDO calculation of NMR chemical shift has been extended. Firstly, it is applied to the calculations of 13C, 13N and 17O shieldings for a series of representative nitrogen- and oxygen-containing compounds. Then several 13C shieldings of the three iron complexes (C 5H 5)Fe(CO) 2CN, (C 5H 4) 2Fe(COH) 2 and (C 5H 4)Fe(CH 2OH) 2 have been evaluated. The theoretical results are in good agreement with the experimental. In addition, it is found that the calculated diamagnetic contributions, σ d(M), of 13C, 15N and 17O atoms exhibit a good linear relationship with the net charge, ρ(M), on these atoms.

Simulation of magnetic moments in a dilute induced-moment Heisenberg magnet

The author considers a diamagnetically diluted induced-moment Heisenberg magnet in which the active sites have a singlet electronic ground state and an excited doublet state. Moments may be induced at the active sites by mixing the doublet into the singlet through a magnetic exchange interaction or an external magnetic field Hz applied parallel to the z direction. The single-ion Hamiltonian describing this system is -H= Sigma ijJijSiSj- Delta Sigma i(Siz)2-Hz Sigma iSiz, where Delta is the single-doublet separation. Using self-consistent mean-field calculations on computer-generated lattices in one, two and three dimensions, and with connectivities z=2, 3, 4, 6 and 8, he studies the distribution of moments at T=0 as a function of the concentration of diamagnetic impurities, the ratio Jij/ Delta and H. When Hz=0, diamagnetic atoms rapidly reduce the value of the mean induced moment, leaving moments of significant size only in regions composed of active sites that are completely surrounded by other active sites. The sensitivity of the lattice towards dilution increases as z increases. The application of Hz compensates to some extent for the effect of the diamagnetic impurities, raising the mean-moment and reducing the variance of the distribution of the size of individual moments.

Orderly structure in the positive-energy spectrum of a diamagnetic Rydberg atom.

We have observed orderly structure in the spectrum of lithium in the range -1\ensuremath{\le}E\ensuremath{\le}+8 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, in magnetic fields of approximately 6 T. The structure resembles series of Rydberg levels converging on Landau levels. Interactions between levels are evident, but the underlying orderly structure raises hopes that a quantum solution to the problem may be feasible. The structure occurs in a regime where the classical motion is believed to be chaotic.

Characterization of copper heterocyclic compounds: X-ray photoelectron spectroscopy study

Several Cu–azole complexes were synthesized by mixing solutions of cupric chloride and an azole ligand at the appropriate metal-to-ligand ratio. The products were isolated as powders and analyzed by elemental analysis, diffuse reflectance Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. Both the bulk and the surface elemental atomic ratios were identical suggesting no surface reconstruction. This paper primarily addresses the radiation effect on the surface composition of the exposed powder. All powders exhibited Cu(2p) line shape typical of paramagnetic copper; no elemental or diamagnetic copper atoms were observed over a very short period of exposure to x radiation. The position and intensity of the Cu(2p) shakeup satellite revealed differences among the complexes that can be attributed to the nature of the azole ligand and to the coordination geometry. Upon exposure to x radiation or electron beam no change was observed in the relative atomic ratios; however, a new peak evolved on the low-binding-energy side of the Cu(2p) suggesting the formation of diamagnetic copper. The evolution of the Cu+1/Cu+2 ratio and the relative intensity of the shakeup satellite suggested that radiation affects the coordination geometry and electronic structure of the surface layers of these complexes.

High resolution laser spectroscopy of Ba Rydberg atoms

The purpose of the present paper is to illustrate some selected aspects of high resolution laser spectroscopy of Rydberg atoms, rather than giving an extensive review of the state of the art. The following topics will be discussed: (i) Excitation and detection of Ba Rydberg atoms with principal quantum numbers up ton≲300; (ii) Stark effect and atomic diamagnetism of high-n Ba Rydberg states in thel-mixing region, (iii) Resonance in singlet-triplet mixing of 6snp1P1 and 6snd1D2 Ba Rydberg states deduced from hyperfine structure measurements.

Diamagnetism of matter and structure of the atom

Diamagnetic properties of matter were investigated on the grounds of the deterministic model of the atom. It is shown that the simple free-fall atomic model can quantitatively describe the atomic diamagnetism. The calculated magnetic susceptibilities of various materials (noble gases: He, Ne, Ar, and ionic molecules: NaCl, KCl and CaCl 2) were found to be in good agreement with the experimental data.

Correspondence of unstable periodic orbits and quasi-Landau modulations.

We study the correlation between modulations in the photoabsorption cross sections of diamagnetic Rydberg atoms and classical periodic orbits in a completely chaotic regime. Extensive quantum-mechanical calculations of photoabsorption cross sections and classical calculations of periodic trajectories are presented. In accordance with the scaling property of the classical Hamiltonian, the photoabsorption cross sections are studied for fixed values of the scaled energy \ensuremath{\varepsilon}=E/${\ensuremath{\gamma}}^{2/3}$ (\ensuremath{\gamma} is the magnetic field strength parameter) as a function of ${\ensuremath{\gamma}}^{\mathrm{\ensuremath{-}}1/3}$. The modulations of the photoabsorption cross sections appear as prominent peaks in the Fourier-transformed cross sections and can be related to periodic classical orbits. The positions of the peaks are given quantitatively by the scaled action along the periodic orbits and the relative strengths of the peaks can be understood qualitatively by considering the geometry of the orbits and the transition involved and the stability of the classical orbits. The one-to-one correspondence between peaks in the Fourier-transformed cross sections and classical periodic orbits applies not only to the traditional quasi-Landau modulation associated with the classical orbit in the plane perpendicular to the field, but also to a large number of further modulations corresponding to topologically different series of periodic orbits. In the completely irregular region around the zero-field threshold, the unstable periodic classical orbits and the observable peaks in the modulated cross sections cannot in general be related to individual eigenstates of the quantum system.

Diamagnetism of the hydrogen atom in the quasi-Landau regime.

Since the discovery of quasi-Landau resonances by Garton and Tomkins [1] the physics of highly excited atoms in static homogenous magnetic fields has attracted much attention [2]. Substantial progress particularly with the hydrogen atom has been achieved in recent years by theoretical [3–11] and experimental [10–14] work. The interest in atomic diamagnetism arises from the fact that even for the hydrogen atom with its purely Coulombic field the Schrbodinger equation is nonseparable in any coordinate system.

Assignment of ESR signals of Escherichia coli terminal oxidase complexes

The ESR signals of all the major components of the aerobic respiratory chain of Escherichia coli were measured and assigned at liquid helium temperature. Cytochrome b-556 gives a weak high-spin signal at g = 6.0. The terminal oxidase cytochrome b-562 · o complex gives signals at g = 6.0, 3.0 and 2.26, and the terminal oxidase cytochrome b-558 · d complex gives signals at g = 6.0, 2.5 and 2.3. A signal derived from cupric ions in the purified cytochrome b-562 · o complex was observed near g = 2.0. It was shown by the effects of KCN or NaN 3 on cytochromes under the air-oxidized conditions that cytochrome o has a high-spin heme and cytochrome d has a low-spin heme. The E′ m values for cytochromes b-558 and d, respectively, determined by potentiometric titration of the ESR signals were 140 and 240 mV in the membrane preparation, and 30 and 240 mV in the purified preparation. The oxidized cytochrome d gave intense low-spin signals at g = 2.5 and 2.3, while cytochrome d under the air-oxidized conditions gave corresponding signals of only very low intensity. These results suggested that most of the cytochrome d under the air-oxidized conditions contains a diamagnetic iron atom with a bound dioxygen.

Nuclear magnetic resonance of rare-earth Van Vleck paramagnets

Theoretical and experimental investigations of nuclear magnetic resonance in rare-earth Van Vleck paramagnetic materials are reviewed. The majority of the observed aspects of the phenomenon is explained by the interaction of nuclei with the residual electronic magnetic moment in the singlet ground state and the modulation of this interaction as a result of the coupling of the electronic moments among themselves and with the oscillations of the crystal lattice, and also by various spin-spin interactions involving enhanced nuclear moments. At liquid helium and higher temperatures the most significant effect is the modulation of the hyperfine interaction resulting from real thermal transitions of Van Vleck ions between the ground state and the nearest excited states. Within the framework of a single simple theory based on the randomly varying in time hyperfine interaction Hamiltonian, a description is given of the temperature dependence of the shifts and widths of NMR lines, of the spin-lattice relaxation times of nuclei within Van Vleck ions and within diamagnetic atoms, and also of the frequency and orientation dependences of these quantities. The theory is in agreement with experiment not only qualitatively, but to a significant extent also quantitatively without resorting to any adjustable parameters. Some special features of nuclear magnetism of Van Vleck paramagnetic materials at ultralow temperatures are also considered.

Simultaneous diamagnetic and Paschen–Back effects in Rydberg series of In(I)

We qualitatively describe magnetic structures in both π- and σ -polarization for In(I) Rydberg series. Two types of shift of Zeeman patterns, proportional to the square of the magnetic field, and ascribable respectively to partial Paschen-Back effect and atomic diamagnetism - previously considered mutually exclusive - are found to occur simultaneously. We attempt quantitative description of this combination.

Direct measurement of the nuclear magnetic dipole moments of 191Ir and 193Ir by high-precision atomic beam magnetic resonance

For the four lowest atomic levels of 191Ir and six levels of 193Ir the hyperfine structure constants A, B, and C were determined by high-precision atomic beam magnetic resonance. Using the triple-resonance technique, ΔM J =0, ΔM I =1 transitions, which depend strongly on the nuclear g I factors, were investigated at magnetic fields up to 2100 Oe, and the following values for the nuclear magnetic dipole moments were deduced: μ I( 191 Ir)=0.1485(6)μ N , μ I( 193 Ir)=0.1613(6)μ N (uncorrected for atomic diamagnetism).

Apparatus for the measurement of the magnetic susceptibility of liquids in high magnetic fields

We describe an apparatus capable of measuring the magnetic force on small liquid samples in high magnetic fields. The apparatus has been used to measure the magnetic susceptibility χ of liquid He at pressures up to 3 MPa in high magnetic fields and has a sensitivity in such measurements comparable to superconducting magnetometers in lower fields. The performance was tested by measuring the atomic diamagnetism of liquid 4He and liquid 3He as well as the nuclear paramagnetism of liquid 3He at 1.2 K in fields up to 15 T.

Theory of the Nuclear Magnetic Resonance Lineshape in Magnetically Diluted Crystals

AbstractThe lineshape of the nuclear magnetic resonance in diamagnetic crystals with paramagnetic impurities is calculated with the help of the Green's function method for the case when both, the nuclear and electron spins are ½. The linewidth and the line shift at slow and rapid fluctuations of the local field produced by the paramagnetic impurities on the nuclei of the diamagnetic atoms magnetic are calculated.

On a possible dynamical symmetry in diamagnetism

Simple theoretical calculations on atomic diamagnetism are presented and compared with heuristic arguments. The existence of exponentially small anticrossings of energy levels in the B field diagram as pointed out recently is confirmed, and tentatively discussed in terms of general theorems of classical mechanics. Conjectures on conservation of nodal surfaces between the low and high field limits are shown to violate our results in the low field Coulomb limit.

Early building up of the quasi Landau spectrum in the diamagnetic coulomb region

We report the results of experimental measurements on atomic diamagnetism in inter-l and inter-n mixing conditions. They have been obtained using high resolution techniques on highly hydrogenic M = ± 3 states of cesium, providing a pure experimental situation. Comparison with straightforward hydrogenic calculations and semi-classical predictions allow identification of the dominant lines of the spectrum which are shown to behave as precursors of the quasi Landau spectrum.