Hydrogen Hyperfine Research Articles

The hydrogen hyperfine structure and inelastic electron proton scattering experiments

It is shown that present experiments on inelastic electron proton scattering can be used to set bounds to part of the proton polarizability contribution to the hyperfine structure of the ground state in the hydrogen atom.

Hydrogen Maser Wall Shift Experiments at the National Research Council of Canada

One of the limiting factors which restrict the hydrogen maser to the role of a secondary frequency standard is the uncertainty in the experimental determination of the wall shift. This paper describes a series of experiments carried out at the National Research Council of Canada, using two hydrogen masers, to investigate the wall shift of five spherical storage bulbs of different diameters, each coated by the same technique with FEP Teflon from the same batch. The theoretically predicted inverse relationship between wall shift and bulb diameter was found to hold experimentally with very small point scatter for all five bulbs. Results showing the dependence of wall shift on bulb diameter and the variation of wall shift with temperature from 23°C to 35°C are given. Measurements made on the largest storage bulb at the beginning and end of the series of experiments allow some estimate to be made of the stability of the wall shift over a period of several months. Measurements indicating a change in wall shift of not more than 2 parts in 1013 over a period of 7 months for a storage bulb transported between Japan and Canada are also discussed. Comparison of the frequency of one of the masers with that of the NRC primary cesium beam frequency standard (Cs III) has given a value of the unperturbed hydrogen hyperfine transition frequency of 1420405751.770 ± 0.003 Hz, which is in satisfactory agreement with the most recent determinations by other workers.

A magnetic resonance spectrometer for studying the recombination decay of atomic hydrogen concentrations using a sampling technique

A magnetic resonance spectrometer operated in a pulse sampling mode has been developed for studying the decay of the atomic hydrogen concentrations in bottles of high purity hydrogen during the intervals between repetitively pulsed rf discharges. The atomic concentrations are obtained by analysing the electron spin-exchange collisional broadening of the absorption resonance signals corresponding to the atomic hydrogen hyperfine transition. The instrument has been used to study atomic hydrogen recombination at glass and quartz surfaces, and has potentialities for use in studies of three body gas phase recombination.

Application of simple theoretical methods to the solution of chemical problems. IV. Hydrogen, carbon-13, and oxygen-17 hyperfine splitting constants in rigid bicyclic semidiones

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of simple theoretical methods to the solution of chemical problems. IV. Hydrogen, carbon-13, and oxygen-17 hyperfine splitting constants in rigid bicyclic semidionesGraham R. Underwood and Veronica L. VogelCite this: J. Am. Chem. Soc. 1971, 93, 5, 1058–1063Publication Date (Print):March 1, 1971Publication History Published online1 May 2002Published inissue 1 March 1971https://doi.org/10.1021/ja00734a002RIGHTS & PERMISSIONSArticle Views27Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (667 KB) Get e-Alerts Get e-Alerts

Measurement of the Unperturbed Hydrogen Hyperfine Transition Frequency

The results of a joint experiment aimed primarily at the determination of the frequency of the H1 hyperfine transition (F = 1, mF = 0) ? (F = 0, mF = 0) is reported. In terms of the frequency of the Cs133 hyperfine transition (F = 4, mF = 0) ?(F = 3, mF = 0), defined as 9192 631 770 Hz, for the unperturbed hydrogen transition frequency the value ?H = 1420 405 751.768 Hz is obtained. This result is the mean of two independent evaluations against the same cesium reference, which differ by 2 × 10-3 Hz. We estimate the one-sigma uncertainty of the value ?H also to be 2 × 10-3 Hz. One evaluation is based on wall-shift experiments at Harvard University; the other is a result of a new wall-shift measurement using many storage bulbs of different sizes at the National Bureau of Standards. The experimental procedures and the applied corrections are described. Results for the wall shift and for the frequency of hydrogen are compared with previously published values, and error limits of the experiments are discussed.

A Method for Eliminating the Wall Shift in the Atomic Hydrogen Maser

The wall shift of the hydrogen maser depends on the collision rate and the average phase shift per collision of the atoms in the storage bulb. By operating at the temperature where the average phase shift per collision is zero it is possible to remove the wall shift. The determination of this temperature is made by measuring the wall shift as a function of temperature for two similarly coated bulbs offering different collision rates to the stored atoms. The intercept of the wall shift vs. temperature curve for the two bulbs-occurs at the zero phase shift per collision temperature. To eliminate the possible differences in wall coatings the use of a flexible storage bulb is recommended.An experimental example of the technique is given using two separate bulbs. The data is in good agreement with a previous measurement of the unperturbed hydrogen hyperfine frequency by H. Hellwig et al.

Electron spin resonance spectrum of the monohydro free radical of 2,3,5,6-tetrachloronitrobenzene

The e.s.r. spectrum of a short-lived radical obtained by the ultra-violet photolysis of 2,3,5,6-tetrachloronitrobenzene in various solvents has been attributed to a monohydrogenated species. The hydrogen hyperfine splitting constants range from 0.38 to 0.50 millitesla. A tentative value of 106 M–1 s–1 has been placed on the upper limit of the second-order decay constant.

Pressure shift of the hydrogen hyperfine frequency by krypton and xenon

Hyperfine pressure shifts for hydrogen atoms in krypton and xenon were measured by optical pumping. Expressed as fractions of the hyperfine frequency, the shifts are (-10.4 ± 0.2) × 10 -9/ Torr(0° C) and (-20 ± 2) × 10 -9/ Torr (0° C). These shifts are not consistent with theory.

Pressure Shifts of Hyperfine Splitting of Hydrogen and Tritium in Argon

This paper reports new measurements of the pressure shifts in argon of the hyperfine splitting of hydrogen and tritium. A spin-exchange optical pumping technique was used to make these measurements. The fractional pressure shift (pressure shift in cps/mm Hg at 0\ifmmode^\circ\else\textdegree\fi{}C divided by the hyperfine splitting in kMc/sec for hydrogen in argon is -4.78 \ifmmode\pm\else\textpm\fi{} 0.03; the ratio of the fractional pressure shift for tritium to that for hydrogen is 1.007\ifmmode\pm\else\textpm\fi{}0.012; the temperature shift at constant density of the hydrogen hyperfine splitting is 0.012\ifmmode\pm\else\textpm\fi{}0.003 cps/\ifmmode^\circ\else\textdegree\fi{}K mm Hg. This new value for the hydrogen pressure shift is then used to reanalyze the Yale data for the hyperfine splitting of muonium, under the hypothesis that the fractional pressure shift for muonium is the same as that for hydrogen. This gives for the muonium hyperfine splitting an alternative value of 4463.23(2) Mc/sec. This value of the muonium hyperfine splitting gives for the fine-structure constant \ensuremath{\alpha} the alternative value ${\ensuremath{\alpha}}^{\ensuremath{-}1}=137.0367(10)$. This value of $\ensuremath{\alpha}$ is compared with the values obtained from the hydrogen fine structure, hydrogen hyperfine structure, and the ac Josephson-effect determination of $\frac{2e}{h}$.

Electron Spin Resonance Study of the Photolytic Decomposition of HN3 in Inert Matrices at 4.2°K

The only paramagnetic species observed amongst the products of the photolytic decomposition of hydrazoic acid, HN3, in Ar, Kr, and Xe matrices at 4.2°K are NH2 and an unidentified species which contains one hydrogen atom and possesses a hydrogen hyperfine coupling constant aHiso=23.8 G and giso∼2.010. The NH2 is probably produced by photolytic decomposition of HN3 aggregates. Our experiments have shown that the production of paramagnetic species is critically temperature dependent as witnessed by the fact that if there is poor thermal contact between the matrix sample and the coolant, then in addition to the above-mentioned paramagnetic species, H and N atoms are also formed. The H and N atoms appear to be formed as a result of the diffusion of NH, the primary product of the photodecomposition of HN3, followed by unidentified secondary processes and not by direct photolytic decomposition of HN3 or NH.

Polarizability Contribution to the Hydrogen Hyperfine Structure

Polarizability Contribution to the Hydrogen Hyperfine Structure

A semi-empirical calculation of hydrogen hyperfine coupling constants in some sigma electron radicals

Spin density distributions in a number of sigma electron radicals have been computed, using the unrestricted Hartree-Fock (UHF) [1] method with the CNDO/2 [2] approximations for the integrals involved. Coupling constants were calculated using simple relationships, and the results in general show good agreement with experiment. Similar calculations on fluorine containing radicals were performed, but core electrons need to be included explicitly to obtain meaningful results.

The Electron Spin Resonance and Electronic Spectra of 4-Substituted Pyridinyl Radicals

Abstract The ESR and electronic absorption spectra have been measured with the 1-methyl-4-carbo-methoxy-, 1-methyl-4-carbamido-, 1-methyl-4-acetyl- and 1-methyl-4-cyanopyridinyl radicals. From the analysis of their ESR spectra by the aid of a spectrum accumulator, we have been able to determine the nitrogen and hydrogen hyperfine splitting constants of these pyridinyl radicals, from which the spin distributions have then been evaluated. These radicals except for the 1-methyl-4-carbamidopyridinyl radical, have been found to show three absorption bands, at 300–350 mμ, at about 400 mμ and at about 600 mμ. From the results of the ESR and electronic absorption spectra, the electronic structures of these pyridinyl radicals have been concluded to be similar to those of the 4-substituted pyridine anion radicals. The preparation of 1,2,6- and 1,3,5-trimethyl-4-substituted pyridinyl radicals has been attempted. The latter radicals, except for the 1,3,5-trimethyl-4-cyanopyridinyl radical, were not detected by the ESR and electronic absorption spectra, because the steric hindrance of the methyl groups at the 3 and 5 positions prevents them from achieving the resonance stabilization due to the 4-substituent.

Electron spin resonance studies of radicals and radical-ions in solution. Part V. Solvent effects on the spectra of mono- and di-phenyl nitric oxide

The radicals mono- and di-phenyl nitric oxide give electron spin resonance spectra in which the nitrogen and hydrogen hyperfine coupling constants vary markedly with solvent. These effects are accounted for by simple molecular orbital calculations using the Huckel and McLachlan methods.

Axial meson exchange and the relation of hydrogen hyperfine splitting to electron scattering

Axial meson exchange and the relation of hydrogen hyperfine splitting to electron scattering

Polarization contribution to the hydrogen hyperfine structure and phenomenology of the electron-proton interaction

In order to understand the significance of the well-known discrepancy of 45 ppm in the hydrogen hyperfine structure we have calculated the polarization correction using an isobar model for the proton, and compared the sensitivity to electron-proton forces of the analysis of the hyperfine splitting with that of the Lamb shift and of electron-proton scattering. A methodological innovation of the calculation is the avoidance of the Rarita-Schwinger formalism for spin 3/2 by the construction of a covariant analytic amplitude from the familiar non-relativistic partial-wave amplitude. It is found that the 3-3 isobar, and by extension higher resonances, are more than an order of magnitude too small to be significant and that the discrepancy is genuine. We consider the introduction of a phenomenological electron-proton interaction term, representing unknown or neglected forces, to account for the discrepancy, and find that this would not necessarily lead to a contradiction with Lamb shift or electron-proton scattering data. We point out that, whatever the cause of the discrepancy, it is likely to be proportional, in percent, to the electron mass, so that it would be roughly 200 times greater in μ-mesic hydrogen (μ−-p) than in hydrogen. We strongly encourage a measurement of the hyperfine splitting of μ-mesic hydrogen, of sufficient accuracy to determine whether the discrepancy is common to both systems and proportional to the lepton mass.

The Atomic Hydrogen Maser

The atomic hydrogen maser is described. In this device hydrogen atoms in the upper hyperfine state are focused onto the entrance aperture of a teflon coated quartz bulb in which the atoms are stored for about a second. This bulb is surrounded by a cylindrical radiofrequency cavity. When the cavity is tuned to the hyperfine frequency of atomic hydrogen, maser radiation is produced. Due to the large line Q resulting from the long storage time, the radiation is highly stable in frequency. Results are given of theoretical calculations on the threshold flux of atoms required for maser oscillations, on the various relaxation processes that limit the effective storage time, and on the possible sources of frequency shifts of the maser. Results are given on the relative stability of two hydrogen masers. Measurements of the atomic hyperfine frequency of atomic hydrogen and deuterium give ΔH = 1,420,405,751.800 ± 0.028 cps and ΔD = 327,384,352.5 ± 1.0 cps on the A.1 time scale with ΔCs = 9,192,631,770.0 cps. The method by which the deuterium has been measured depends upon the effect of a deuterium magnetic resonance transition upon the intensity of the hydrogen maser oscillation amplitude when a mixture of hydrogen and deuterium is used. This method should be capable of extension to a number of different atoms. The hydrogen maser apparatus has been used to measure the spin exchange collision cross section between atomic hydrogen and a number of different gases. Results of some of these measurements are reported. Measurements of the dependence of the hydrogen hyperfine frequency upon a strong externally applied electrostatic field are given.

Stark Shift of the Hydrogen Hyperfine Separation

Stark Shift of the Hydrogen Hyperfine Separation

Electron spin resonance spectra of irradiated monofluoracetamide

The radical trapped in x-irradiated monofluoracetamide is shown to be CHF CONH2 by electron spin resonance studies. The principal values of the hydrogen hyperfine coupling are -96, -63 and -31 Mc/s and of the fluorine coupling are +530, -11 and -45 Mc/s. The relative signs of the principal couplings were established, using a spectrometer operating at 35 000 Mc/s which is briefly described. The differences in spectra between measurements at 9000 Mc/s and at 35 000 Mc/s are indicated. Finally the couplings are interpreted and shown to be consistent with Huckel parameters for fluorine with (αF-αC) = 2·4βC-F.

The Electron Spin Resonance and Electronic Spectra of the Anion Radicals of 4-Nitropyridine and 4-Nitropyridine 1-Oxide

Abstract The ESR and electronic spectra of the 4-nitropyridine and 4-nitropyridine 1-oxide anions have been measured. The nitrogen and hydrogen hyperfine splitting constants of these two compounds have been determined. In order to analyze the ESR spectra exactly, the measurements have also been carried out with respective compounds containing 15N instead of 14N in the nitro group. The spin densities on the nitrogen and carbon atoms of these two anions have been estimated from the splitting constants. It has thus been found that the spin densities on the ring nitrogen and carbon atoms are undoubtedly larger in the 4-nitropyridine 1-oxide anion than in the 4-nitropyridine anion. The electronic spectrum of the 4-nitropyridine anion has been measured and three peaks found at 313, 440 and 640 mμ. According to the molecular orbital calculations carried out with the π-electron system of the 4-nitropyridine anion, it has been concluded that the 440 mμ band may be regarded as the intramolecular charge transfer band, and that the 313 mμ band can be interpreted as the blue shifted band of the pyridine anion.