Hyperfine Structure Of Hydrogen Research Articles

On the possibility of detecting a global signal in the line of the hyperfine structure of hydrogen from the Dark Ages

On the possibility of detecting a global signal in the line of the hyperfine structure of hydrogen from the Dark Ages

EPR characterization in natural quartz samples of a newly discovered hydrogen related defect and already known germanium related defects

The role of hydrogen in the formation and modification of defects in quartz is well known, but still to be clarified is its involvement in trapping and recombination properties of quartz on which its dating characteristics are based. In this work, we studied the thermal stabilities of EPR signals in natural pegmatitic quartz using an X-band spectrometer. We also observed at least two previously unreported EPR signals in quartz, one of them possessing a hydrogen hyperfine structure with large coupling constant. Its thermal stability is intermediate between the well-known [GeO4]- and [GeO4/Li+]0 centres, while the other newly reported signals possess a thermal stability comparable to the latter. The sample has been further studied with a Q-band spectrometer to enhance the resolution of the spectrum. This allowed to confirm, without having to fit or simulate the overlapped signals, the g-factors reported in the literature for Ge related centres, which are strongly overlapped in the X-band. We performed simulations to extrapolate the g-factors and coupling constants of the observed components. We carried out pulse annealing experiments to determine the trap depth of the centres originating such signals. The hydrogen related centre signal has been simulated with the g-tensor's main components being g1 = 2.0007, g2 = 1.9974 and g3 = 1.9929, with coupling constants A1 = 233 MHz, A2 = 235 MHz and A3 = 239 MHz, and trap depth of 1.14 eV.

Intergalactic Heating by Lyα Photons Including Hyperfine Structure Corrections

Abstract Lyα photons from the first radiating sources in the universe play a pivotal role in 21 cm radio detections of Cosmic Dawn and the Epoch of Reionization. Comments are provided on the effect of the hyperfine structure of hydrogen on the rate of heating or cooling of the Intergalactic Medium by Lyα photons.

A LABORATORY STUDY OF C 3 H + AND THE C 3 H RADICAL IN THREE NEW VIBRATIONALLY EXCITED 2 Σ STATES USING A PIN-HOLE NOZZLE DISCHARGE SOURCE

Rotational lines of the positive molecular ion C3H+ and of the neutral C3H radical in three new vibrationally excited states with 2Σ symmetry have been detected in a supersonic molecular beam in the centimeter-wave band. The fundamental rotational line of the ion is quite weak, but is observed with similar intensity in a dc discharge through several different hydrocarbon gases when helium is the buffer gas. Under these conditions, the fractional abundance of C3H+ relative to C3H is estimated to be of order 10−4, i.e., toward the lower end of the ratio (10−3–10−4) found for protonated ions using the same discharge nozzle. For each new 2Σ state of the C3H radical, spectroscopic constants, including those describing hydrogen hyperfine structure, have been determined to high precision. Lines of one 2Σ state (B = 11271 MHz) are particularly intense in our molecular beam; for this state and a second one (B = 11306 MHz), millimeter-wave transitions have also been observed between 180 and 340 GHz using a long path dc glow absorption spectrometer. On the basis of intensity measurements with this spectrometer, the inferred rotation–vibration constant α, and theoretical calculations, the state with B = 11271 MHz is tentatively assigned to the ν5 bending mode, predicted to lie ∼300 cm−1 above ground.

Baryon Structure and Electromagnetic Properties

We seek dynamical consequences of the assumption that the baryon is composed of slowly moving heavy objects (quarks). It is found that the hyperfine structure of hydrogen is relativity sensitive to structure, and the effect tends to reduce the present discrepancy between theory and experiment. It is also pointed out that all neutral baryons will have vanishing charge form factors according to the present model.

Electron spin resonance of palladium-related defect in silicon

Abstract A different Pd-related defect from a substitutional Pd with (C2v) symmetry was detected by ESR measurement. New ESR signal of the Pd-related defect showed different g-value and symmetry from those of the substitutional Pd. The Pd-related defect has anisotropic character of monoclinic (C1h) symmetry. The calculated g-values are g1=1.97, g2=2.03, g3=2.16, and the g1 axis is along 〈1 1 0〉 direction. The g2 and g3 axes are perpendicular to the g1 axis, and the g2 axis is rotated from 〈1 0 0〉 to 〈1 1 1〉 direction at the angle of 51°. In addition to the Pd-related defect, we have found other ESR signals in Pd and hydrogen-diffused Si. The ESR signals showed the hyperfine structure of hydrogen. Therefore, it is though that the ESR signals are originated from Pd–H complex defect.

A laboratory and theoretical study of silicon hydroxide SiOH

The rotational spectrum of the triatomic free radical SiOH in its X (2)A(') ground electronic state has been observed in a supersonic molecular beam by Fourier transform microwave spectroscopy. The fundamental (1(0,1)-->0(0,0)) transition has been detected for normal SiOH and for three rare isotopic species: (30)SiOH, Si(18)OH, and SiOD. The same transition has also been observed in two of three excited vibrational states, v(2) and v(3), for the most abundant species. Precise spectroscopic constants, including those that describe the effective spin doubling and hydrogen hyperfine structure, have been derived for each isotopic species or vibrational state. To complement the laboratory work, theoretical calculations of the structure, dipole moment, and energies of the X (2)A(') and low-lying 1 (2)A(") states have also been undertaken at the coupled cluster level of theory. In agreement with theoretical predictions, we conclude from the hyperfine constants that SiOH is a best described as a pi-type radical, with the unpaired electron localized on a p orbital on the silicon atom. Assuming a bond angle of 118.5 degrees , the Si-O bond length is 1.647(2) A and the O-H bond length is 0.969(4) A.

Experimental Constraints on Polarizability Corrections to Hydrogen Hyperfine Structure

We present a state-of-the-art evaluation of the polarizability corrections--the inelastic nucleon corrections--to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value Delta(pol)=1.3+/-0.3 ppm. This is 1-2 ppm smaller than the value of Delta(pol) deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits.

Cumulative “roof effect” in high-resolution in vivo 31P NMR spectra of human calf muscle and the Clebsch–Gordan coefficients of ATP at 1.5 T

NMR spectra of non-weakly coupled spin systems exhibit asymmetries in line intensities known as “roof effect” in 1D spectroscopy. Due to limited spectral resolution, this effect has not been paid much attention so far in in vivo spectroscopy. But when high-quality spectra are obtained, this effect should be taken into account to explain the quantum-mechanical fine structure of the system. Adenosine 5′-triphosphate (ATP) represents a 31P spin system with multiple line splittings which are caused by J-couplings of medium strength at 1.5 T. We analyzed the ATP roof effect in vivo, especially for the β-ATP multiplet. The intensities of its outer resonances deviate by ca. 12.5% from a symmetrical triplet. As this asymmetry reflects the transition from Paschen–Back to Zeeman effect with total spin that is largely broken up, the Clebsch–Gordan coefficients of the system can be indicated in analogy to the hyperfine structure of hydrogen. Taking the roof effect into account, the χ 2 of fitting in vivo ATP resonances is reduced by ca. 9% ( p < 0.005).

On the Emergence of a Polychromatic Photon from a Single Atom

Recent attempts to establish a space-time description of single-photon emission from single atoms (or molecules) are reviewed. In the wake of historical remarks on the so-called Lorenz zone of molecular influence, characteristics of the power-law confined birth domain of the photon are discussed within the framework of a field-unquantized formalism. In contrast to the common believe it is shown that the birth domain can be (and is) exponentially localized if the photon emerges from a pure spin transition. As a paradigm of exponential localization we discuss the emergence of a radio-frequency photon from the hydrogen hyperfine structure. Starting from the first-quantized description of the energy wave function of a polychromatic photon in vacuo, we introduce a propagator description of the photon embryo, and argue that the single-photon tunnelling process is a fingerprint of our inability to localize photons in space-time. With this understanding optical tunnelling appears as an indispensable part of all single photon-atom scattering processes. In the final part of the review we briefly describe how the formalism can be upgraded from single-photon wave mechanics to a field-quantized description based on wave packet (wave train) electrodynamics. In this new formalism, in which the polychromatic photon embryo is included as an integral part of the polychromatic field quanta, the electrons of the atom (or molecule) move not only in the self-consistent Coulomb potential but also in the transverse potential created by the particles themselves. A rigorous relativistic quantum electrodynamic theory of wave train photon emission from single atoms emerges in the horizon.

Hyperfine structure in hydrogen and helium ion

QED theory of the hyperfine splitting of the $1s$ and $2s$ state in hydrogen isotopes and helium-3 ion is considered. We develop an accurate theory of a specific difference 8E_{HFS}(2s)-E_{HFS}(1s). We take into account fourth order corrections and nuclear structure effects. The theoretical prediction is now of a higher accuracy than the experiment is. The study of the difference provides the most accurate test (on a level of a part in 10^8) of the QED theory of $1s$ HFS up to date. The theory agrees with most of the experimental data.

Comparative EPR study of hydrogenated and unhydrogenated amorphous silicon carbide thin films

In this work, electron paramagnetic resonance (EPR) is used to study paramagnetic centers in stoichiometric hydrogenated a-SiC:H synthesized by plasma enhanced chemical vapor deposition (PECVD) and unhydrogenated a-SiC grown by pulsed laser deposition. While the spin density of the a-SiC films was determined to be of the order of 10 20 spins/cm 3, it was found to be more than one order of magnitude lower (10 19 spins/cm 3) for the as-deposited a-SiC:H films and decreases to less than 10 17 spins/cm 3 upon annealing at 650 °C. For both types of films, the dominant paramagnetic centers in the films are carbon related defects, as deduced from the g-value of the EPR signal. The PLD a-SiC films have a symmetric exchange narrowed Lorentzian EPR line that indicates some clustering of the spins. For a-SiC:H films, the EPR shows some asymmetry that is probably due to the presence of silicon related defects in the layers. No evidence of spin clustering was found for a-SiC:H and the EPR linewidth is most likely determined by dipolar interaction and some unresolved hydrogen hyperfine structure for the as-deposited and annealed a-SiC:H films, respectively. The temperature dependence of the EPR linewidth for both types of films and the power saturation behavior of the EPR signal are also presented and discussed.

Some possibilities for laboratory searches for variations of fundamental constants

We consider different options for the search for possible variations of the fundamental constants. We give a brief overview of the results obtained with several methods. We discuss their advantages and disadvantages with respect to simultaneous variations of all constants in both time and space in the range 108–1010 years. We also suggest a few possibilities for the laboratory search. Particularly, we propose some experiments with the hyperfine structure of hydrogen, deuterium, and ytterbium–171 and of some atoms with a small magnetic moment. Other suggestions are for some measurements of the fine structure associated with the ground state. Special attention is paid to the interpretation of the hfs measurements in terms of variations of the fundamental constants. PACS No.: 31.30G

Some possibilities for laboratory searches for variations of fundamental constants

We consider different options for the search for possible variations of the fundamental constants. We give a brief overview of the results obtained with several methods. We discuss their advantages and disadvantages with respect to simultaneous variations of all constants in both time and space in the range 10^{8}-10^{10} yr. We also suggest a few possibilities for the laboratory search. Particularly, we propose some experiments with the hyperfine structure of hydrogen, deuterium and ytterbium-171 and of some atoms with a small magnetic moment. Other suggestions are for some measurements of the fine structure associated with the ground state. Special attention is paid to the interpretation of the hfs measurements in terms of variations of the fundamental constants.

Electron paramagnetic resonance characterization of nonuniform distribution of hydrogen in silica optical fibers

The hydrogen distribution within low-OH silica optical fibers has been characterized by electron paramagnetic resonance in combination with a chemical etch-back technique. The 74 G doublet, the signal generated by a hydrogen hyperfine structure of the Si E′ center, was used to investigate the spatial distribution of hydrogen reaction products in silica optical fiber and, in particular, the reaction between the twofold coordinated silicon and hydrogen. A nonuniform distribution of the 74 G species was observed with the highest concentration near the fiber surface, indicative of a corresponding nonuniform distribution of hydrogen. The polymer fiber coating appears to be the primary source of the trace amounts of hydrogen observed in the silica fibers.

Singularities in the fields of electric and magnetic multipoles and related identities involving the Dirac delta function

The nature of the field at the site of electric and magnetic point dipoles is examined in detail. As is well known, different singularities arise when the magnetic point dipole is considered as the limit of a small current loop or when it is obtained by the juxtaposition of two magnetic point charges. The singularities in the field have a direct measurable effect in the hyperfine structure of hydrogen. They also play a role in the discussion of macroscopic magnetic and electric fields in matter. We develop a new procedure based on an extension and generalization of the Dirac delta formalism which allows for the confluence of singularities. The method generates the singularities in a direct and systematic way and is applied to the calculation of the electric and magnetic fields of discrete and continuous multipolar distributions.

ESR and ENDOR Investigations of Adrenochrome Semiquinone and Related Amino-1,2-Benzosemiquinone Radicals

Abstract Dimethyl or diethylamine reacts very smoothly in ethanol solution with catechols to the corresponding aminoquinones. The paramagnetic intermediates, the semiquinones, are investigated by ESR and ENDOR spectroscopy using the spin stabilisation technique with diarylthallium cations. The spectra of these radicals show clearly the thallium and nitrogen coupling and the hydrogen hyperfine structure. For some examples the signs of the proton coupling constants are determined by TRIPLE resonance experiments. The results indicate a negative spin density in one position of the unsymmetrically substituted radical 3. With the results obtained for the monocyclic aminosemiquinones the hyperfine structure of the adrenochrome semiquinone is analysed.

Paramagnetische ionenpaare als vorstufen bei der synthese von zinn(IV)-sauerstoffheterocyclen

Triorganyltin hydroxides react with catechols in organic solvents in the presence of air oxygen at first to paramagnetic complexes which are investigated by ESR spectroscopy. The reaction has been run using 6 catechols and 5 different organometallic compounds in numerous solvents, so that its general application is proved. The ESR spectra of the solutions show typical hydrogen hyperfine structure and large splittings, which have to be assigned to magnetic coupling of the free electron with 117Sn and 119Sn nuclei. The tin splittings and the g-values significantly depend on the temperature and the solvent. These observations are interpreted in terms of ion pairing effects. A quantitative interpretation is given. The final products of these reactions are diamagnetic compounds which can be isolated in good yields. Based on the elemental analysis, 1H NMR and mass spectroscopy (electron impact, field desorption), the structures are assigned of partly dimerised o-phenylene dioxystannanes.

A novel method for the structural and configurational analysis of alkyl 3,4,6-tri- O-acetyl-2-deoxy-2-hydroxyimino-α- d- arabino- and- lyxo-hexopyranosides, using E.P.R. spectroscopy

Alkyl 3,4,6-tri- O-acetyl-2-deoxy-2-hydroxyimino-α- d- arabino- and -lyxo-hexopyranosides were oxidised with lead(IV) acetate in solution, yielding the corresponding Z- and E-isomeric iminoxy radicals ( > CNO), which gave very intense and persistent electron paramagnetic resonance (e.p.r.) signals. Applyina previous results for cyclohexane iminoxy radicals and the differences between the spectra of the arabino and lyxo compounds, it has been possible to assign the observed, hydrogen hyperfine structure for both Z- and E-radicals to the hexopyranoid-ring hydrogen atoms at C-1,3,4, and 5 or 6. From Z- and E-oximes, the same Z/E-equilibrium mixture of iminoxy radicals is obtained. Also, conclusions on the conformation of the hexopyranoid ring have been drawn, based on solvent and temperature effects. The specificity and sensitivity ofthe novel e.p.r. method have been used to characterise α- d-oximes in μg-amounts in t.l.c. The presence of other (mainly β) oximes has also been demonstrated.

Paramagnetische organothalliumverbindungen in lösung: I. Esr-untersuchungen von diphenyl-thallium(III)-tonenpaaren mit brenzcatefechinen, pyrogallolen und 1,2-diketonen

Diphenylthallium hydroxide reacts very smoothly in organic solvents with catechols, pyrogallols and 1,2-diketones to stable paramagnetic diphenylthalliumsemiquinone and diphenylthalliumsemidione complexes respectively. This reaction has been investigated with 43 different ligands in numerous solvents. Therefore its general application is proofed. The ESR-spectra of these solutions show the hydrogen hyperfine structure of the ligands and an unusual large coupling which we assign to magnetic interaction of the free electron with the 203Tl and 205Tl nuclei. The thallium splittings observed depend remarkably on the ligands used. We refer this to different solvation phenomena. Semiquinones of the pyrogallol type show on principle two different radical types. Small concentrations of diphenylthallium hydroxide produce 1 1 complexes. These can be converted into 1 2 complexes by addition of further amounts of diphenyl thallium hydroxide. The ESR-spectra of the semiquinone-and the semidione-thallium complexes exhibit an unusually strong solvent dependence of the thallium coupling and of the g-factor. It is possible to explain both variations uniformly by the different donor ability of the solvents used. All complexes investigated indicate remarkable temperature dependence of the thallium splitting and the g-factor. The thallium couplings show a positive temperature gradient whereas the g-factor decrease with increasing temperature as expected. Based on the sum of the observed effects, we assume that the radicals observed by us are ion pairs in which a diphenylthallium cation interacts with the semiquinone- or semidione-anion, respectively.