Hyperfine Properties Research Articles

ChemInform Abstract: Exchange Coupling and Resonance Delocalization in Reduced (Fe4S4)+ and (Fe4Se4)+ Clusters. Part 1. Basic Theory of Spin‐State Energies and EPR and Hyperfine Properties

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The dipole moment of water. I. Dipole moments and hyperfine properties of H2O and HDO in the ground and excited vibrational states

Molecular beam electric resonance spectroscopy has been used to study H2O in its ground state and in each of its singly excited vibrational states. HDO was studied in its ground state and first excited O–H stretching state. Precise dipole moments have been obtained for a total of 14 rotational levels of six vibrational states. Centrifugal distortion corrections to the Stark coefficients were made and rotationless moments were calculated for each vibrational state. The magnitude of the H2O moment can be written μ(v1v2v3) =1.857 04+0.005 08(v1+ (1)/(2) ) −0.031 66(v2+ (1)/(2) ) +0.022 46(v3+ (1)/(2) ). Individual components of the HDO moment were obtained for the ground and excited states. Hyperfine properties were also determined for each of the vibrational states studied. In the following paper, the dipole moments are combined with infrared transition moments to obtain an improved dipole moment function for water.

Exchange coupling and resonance delocalization in reduced iron-sulfur [Fe4S4]+ and iron-selenium [Fe4Se4]+ clusters. 2. A generalized nonlinear model for spin-state energies and EPR and hyperfine properties

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExchange coupling and resonance delocalization in reduced iron-sulfur [Fe4S4]+ and iron-selenium [Fe4Se4]+ clusters. 2. A generalized nonlinear model for spin-state energies and EPR and hyperfine propertiesLouis NoodlemanCite this: Inorg. Chem. 1991, 30, 2, 256–264Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://doi.org/10.1021/ic00002a020RIGHTS & PERMISSIONSArticle Views219Altmetric-Citations67LEARN 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 (993 KB) Get e-Alerts Get e-Alerts

Exchange coupling and resonance delocalization in reduced iron-sulfur [Fe4S4]+ and iron-selenium [Fe4Se4]+ clusters. 1. Basic theory of spin-state energies and EPR and hyperfine properties

Exchange coupling and resonance delocalization in reduced iron-sulfur [Fe4S4]+ and iron-selenium [Fe4Se4]+ clusters. 1. Basic theory of spin-state energies and EPR and hyperfine properties

Spin-Polarized Relativistic Band Structure Calculations for Dilute and Concentrated Disordered Alloys

ABSTRACTApplications of the spin-polarized relativistic version of multiple scattering theory (SPRKKR) to study the electronic properties of dilute and concentrated disordered alloys are presented. This approach, developed recently, allows to investigate magnetic systems containing heavy elements and also gives access to a detailed discussion of phenomena, which are linked to the simultanous presence of spin-polarisation and spin-orbit coupling. This is demonstrated by discussing the hyperfine properties of 5d-transition metals dissolved substitutionally in Fe, where pronounced relativistic effects could be found. In addition the magnetic X-ray dichroism (MXD), denoting the difference in absorption of left and right circularly polarized radiation, is studied for these dilute alloys.To be able to deal also with concentrated alloys, we have combined the Coherent Potential Approximation (CPA) alloy theory with the SPRKKR-formalism. Results for the spin-orbit induced orbital contributions to the magnetic moments as well as the MXD in FexCol-x and CoxPtl-x clearly show that remarkable relativistic effects are present even for relatively light elements.

Theory of hyperfine interactions in aqueous Mn3+-porphyrin system

The electronic structure and associated magnetic hyperfine properties of Mn3+-porphyrin with two ligand water molecules are studied using the Unrestricted Hartree-Fock procedure with an aim to understand the observed anomalous water proton relaxivity associated with Mn3+ (TPPS4). Our results show that the electron spin distribution is strongly localized on the metal ion and the point dipole model seems to be a good approximation for the dipolar hyperfine interactions in this system. It appears that the anomalous relaxivity observed in the Mn3+ (TPPS4) is not due to the strong delocalization of the spin distribution associated with the metal ion and may result from unusual dynamical effects.

Theory of14N nuclear quadrupole interaction in pyrrole, indole and carbazole

As a test of the accuracy of the Hartree-Fock Cluster procedure which is being increasingly used for the study of electronic structures and hyperfine properties of solid state systems, we have applied it to study the14N quadrupole coupling constants of the free molecules pyrrole, indole and carbazole, which have been measured by microwave spectroscopic techniques. Our results explain the experimental trends over the three molecules and provide very good quantitative agreement with experiment.

Comparison of hyperfine properties of halosilanes by two different cluster procedures

For purposes of comparison of the accuracies of the Hartree-Fock Cluster and Discrete Variational Method Cluster procedures currently in use for investigation of hyperfine properties of solid state systems, we have studied by both procedures the nuclear quadrupole interactions and silicon-halogen bond distances in the monohalosilane systems SiH3X(X=F, Cl, Br and I). Very good agreement is found between the results by the two procedures and with experiment.

Geometrical arrangement of water molecules in copper–aquoion complex—Influence on shifts and relaxivities in nuclear magnetic resonance

The unrestricted Hartree–Fock cluster procedure has been applied to the Cu2+–(H2O)6 complex to study both its geometry and the hyperfine properties of protons and 17O nuclei in the water molecules of the first hydration sphere. The geometry was studied to understand the Jahn–Teller effect expected for this complex and to explain the observed tetragonal distortion of an elongated nature from extended x-ray absorption fine structure measurements involving four of the H2O molecules being closer to the Cu2+ ion than the other two. The hyperfine properties were studied to attempt to explain observed data in this respect from nuclear magnetic resonance measurements. Our results for the situation in which there is a hole in the dx2–y2 type of state do explain the elongated nature of the tetragonal distortion. The calculated electronic wave functions provide a satisfactory explanation of the 17O hyperfine interaction. For the protons, our results demonstrate the validity of the point ion model commonly used for the dipolar interaction between protons of the hydrated H2O molecules and the unpaired spins in explaining proton nuclear magnetic resonance relaxation data for aquoions. For the proton contact interaction however, theory appears to lead to a higher value than experiment. Possible sources that can lead to an improvement in the predicted proton hyperfine interaction constant are discussed.

An a b i n i t i o study of the magnetic hyperfine properties of F−2(2Σ+u)

Gaussian basis sets derived from the new Dunning ‘‘correlation consistent’’ sets have been used in conjunction with multireference single- and double-excitation configuration interaction (CI) wave functions to determine the magnetic hyperfine properties of the F−2 radical anion and the electron affinity of F2. The best computed values, using an extension to the polarized, valence quadruple zeta basis (cc-pVQZ) are: Aiso(19F)=772 MHz (expt=785 MHz), Adip=890 MHz (expt=901 MHz), and EA=2.61 eV (expt=3.08±0.10 eV). Estimates which crudely account for basis set incompleteness and CI truncation lead to the following, slightly different, values: Aiso (19F)=802 MHz, Adip =898 MHz, and EA=2.94 eV. The sensitivity of Aiso to changes in the F–F bond length results in an uncertainty on the order of ±20 MHz in the isotropic hyperfine property. Such close agreement between theory and experiment suggests that any rare gas matrix effect in the recent electron spin resonance (ESR) measurements on F−2 should be small, i.e., the matrix results should agree well with any future gas phase values. Correlation effects beyond the standard singles and doubles level are estimated to contribute approximately 50 MHz (∼30%) of the 155 MHz correlation correction to Aiso.

ChemInform Abstract: Electric Dipole Moment and Hyperfine Properties of Bromoacetylene in the Ground and First Excited C-H Stretching Vibrational States.

ChemInformVolume 21, Issue 20 Physical Organic Chemistry ChemInform Abstract: Electric Dipole Moment and Hyperfine Properties of Bromoacetylene in the Ground and First Excited C-H Stretching Vibrational States. S. M. BASS, S. M. BASS Dep. Chem., Univ. Rochester, Rochester, NY 14627, USASearch for more papers by this authorR. L. DELEON, R. L. DELEON Dep. Chem., Univ. Rochester, Rochester, NY 14627, USASearch for more papers by this authorJ. S. MUENTER, J. S. MUENTER Dep. Chem., Univ. Rochester, Rochester, NY 14627, USASearch for more papers by this author S. M. BASS, S. M. BASS Dep. Chem., Univ. Rochester, Rochester, NY 14627, USASearch for more papers by this authorR. L. DELEON, R. L. DELEON Dep. Chem., Univ. Rochester, Rochester, NY 14627, USASearch for more papers by this authorJ. S. MUENTER, J. S. MUENTER Dep. Chem., Univ. Rochester, Rochester, NY 14627, USASearch for more papers by this author First published: May 15, 1990 https://doi.org/10.1002/chin.199020053AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue20May 15, 1990 RelatedInformation

Laser vaporization/rare gas matrix-isolation electron spin resonance studies of PdH+2, PdD+2, PdH, and PdD: Theoretical investigation of PdH+2

The reactive laser vaporization of palladium metal in the presence of H2(g) has been used to generate and trap neutral and charged palladium hydride radicals in neon and argon matrices for electron spin resonance investigations. The radicals identified are: 0PdH+2, 105PdH+2, 0PdD+2, 105PdD+2, 0PdH, 0PdD, 105PdH, and 105PdD. The electron spin resonance results prove that the H atoms are equivalent in PdH+2 but it cannot be determined for certain whether a highly bent 2A1 ground state complex or a linear 2Σ state is being observed, although the evidence seems to favor the 2A1 state. The observed nuclear hyperfine properties (A and g tensors) are best accounted for by assigning the unpaired electron predominantly to 4d2z/5s orbitals on the metal in PdH+2 with only about 3% of the spin density on each H atom. Electron spin resonance results for PdH constitute the first observations for a diatomic metal hydride radical trapped in a neon matrix. The magnetic parameters (MHz) for 105PdH+2 in a neon matrix at 4 K are: g⊥=2.568(2); g∥≂1.92; A⊥(105Pd)=−713(2); A∥(105Pd)=−688(15); A⊥(H)=45(1). Multireference SCF (MCSCF) and configuration interaction (CI) calculations were conducted for PdH+2 to calculate the energies and gross population distributions in the lowest-lying electronic states. The lowest of these, the 2A1 state, has a calculated stabilization energy of 9.3 kcal/mol relative to Pd+(4d9)+H2.

Electric dipole moment and hyperfine properties of bromoacetylene in the ground and first excited C–H stretching vibrational states

Molecular beam electric resonance spectroscopy, combined with color center laser excitation, has been used to measure the electric dipole moment and Br hyperfine properties of bromoacetylene in its ground and first excited C–H stretching vibrational states. For the HCC79Br, v=0: μ=0.229 62(1) D, eQq=648.113(3) MHz, CBr=6.4(3) kHz, and B=4000.07 MHz. For the HCC79Br, v=1: μ=0.248 82(1) D, eQq=648.160(2) MHz, CBr=7.0(3) kHz, and B=3992.79 MHz. For the HCC81Br, v=0: μ=0.229 56(1) D, eQq=541.430(1) MHz, CBr=7.4(1) kHz, and B=3978.46 MHz. For the HCC81Br, v=1: μ=0.248 61(1) D, eQq=541.464(3) MHz, CBr=7.6(4) kHz, and B=3971.34 MHz. The vibrational band origin for the C–H stretching vibration is 3367.7(2) cm−1.

Laser vaporization generation of 69Ga31P+ and 71Ga31P+ for neon matrix electron spin resonance studies: Electronic structure comparison with GaAs+

The 69GaP+ and 71GaP+ molecular ions have been generated by the combined methods of photoionization/laser vaporization for trapping in neon matrices at 4 K for electron spin resonance (ESR) investigation. The ground electronic state of GaP+ has been determined as X 4∑ and its electronic structure based on nuclear hyperfine properties is compared with the isovalent ion, GaAs+. The magnetic parameters (MHz) for Ga31P+ are: g⊥ =1.9836(5); A⊥ (69Ga)=188.6(1); A⊥ (71Ga)=239.4(1); A∥ (69Ga)=260(30); A∥ (71Ga)=300(10); A⊥ (31P)=108.0(1); and A∥ (31P)≊200(150). The g and A values observed for 31P(4S1/2) atoms in these neon matrices show closer agreement with the gas phase parameters compared to previous values reported for the heavier rare gases.

Theory of structure and hyperfine properties of anomalous muonium in elemental semiconductors: Diamond, silicon, and germanium.

A number of possible models for the anomalous muonium (${\mathrm{Mu}}^{\mathrm{*}}$) center in the elemental semiconductors diamond, silicon, and germanium are investigated in detail, both with respect to their stabilities and abilities to explain the extensive available experimental hyperfine-interaction data, the latter being the major focus of the present work. Using the unrestricted Hartree-Fock cluster procedure, the electronic structures and potential-energy curves associated with muon positions are obtained for the different models. The results are utilized to obtain hyperfine properties associated with the muon and its neighboring nuclei, including vibrational effects associated with the muon. Our results show that stability considerations favor both the vacancy-associated (VA) and bond-centered (BC) models for ${\mathrm{Mu}}^{\mathrm{*}}$. The VA model explains all the experimentally observed features of the muon hyperfine properties and provides reasonably good quantitative agreement with experiment. However, questions remain regarding its formation and ability to explain level-crossing resonance (LCR) data. On the other hand, although the BC model appears to explain the experimental features from LCR measurements, in its present form, it seriously overestimates the strengths of the muon hyperfine interactions as compared to experiment, by more than an order of magnitude in some cases. Additionally, it does not explain the trend from diamond through germanium. On the basis of the results in this paper for the VA and BC models, the direction for future investigations for understanding the nature of the ${\mathrm{Mu}}^{\mathrm{*}}$ center is commented on.

Electronic structure of azidomyoglobin and associated magnetic and hyperfine properties

The electronic structure of azidomyoglobin has been investigated for understanding the observed magnetic and hyperfine properties of this system. The results of our investigation show that a configuration with five electrons in d-like molecular orbital states, as in the case of ferricytochrome c but unlike nitrosylhemoglobin, provides a satisfactory explanation of the observed strongly rhombic g-tensor, the 57m Fe quadrupole splitting from Mossbauer measurements and the porphyrin 14N quadrupole interactions. For the magnetic hyperfine interactions of the 57m Fe and porphyrin 14N nuclei, there are significant differences between theory and experiment. For the 57m Fe nucleus, after incorporating the influence of spin-orbit effects, which leads to unquenching of the orbital angular momentum through admixture of excited state configurations to the ground state one, very good agreement is found with single crystal Mossbauer data. For 14N hyperfine interactions associated with the pyrrole group however, where spin-orbit effects are expected to be much less pronounced, the theoretical values of the hyperfine constants are found to be less than a fifth of those derived from ENDOR measurements. It is suggested that the difference between theory and experiment could be bridged through incorporation of exchange polarization contribution to the 14N hyperfine interaction from the sizeable valence electron spin density (about 65 per cent of the total) on the iron atom. The need for additional experimental measurements is pointed out, among them ENDOR measurements to determine the hyperfine properties of the azide nitrogens for which the end nitrogens are predicted from the present work to have sizeable magnetic hyperfine constants (about −10 MHz).

Mössbauer study of the hyperfine and magnetic properties of organo-di-iron electron reservoirs containing a polyaromatic bridging ligand

Organo di-iron electron reservoirs Fe(CP*)2(Ar)n+ withn=2, 1, 0, where Cp* is C5(CH3)5 and where Ar are the following bridges: biphenyl, dihydrophenanthrene, triphenylene, have been studied by Mossbauer spectroscopy in the solid state. Complexes withn=2, with 36e− in the coordination spheres of the metals, exhibit the usual diamagnetic behaviour of 18e−, FeII mono-iron systems. Complexes withn=1, 37e−, are delocalized mixed valence (FeIIFeI) with a spin 1/2; the magnetic hyperfine interaction, measured under an external field, shows equal delocalization of the 37th e− on the two iron centers and the two bridging carbon atoms of the biphenylene. Complexes withn=0, formally with 38e−, have a practically temperature-independent quadrupole splitting, and isomer shift values which constrast with the expected behaviour of independent FeI, 19e− centers. This indicates that the 37th and 38th electrons are mostly located on the polyaromatic bridge. Spectra obtained in an external field show a negligible magnetic hyperfine interaction and support this conclusion. In the case of biphenyl and dihydrophenanthrene bridges, this electron localization can be related to a strong intramolecular chemical coupling, evidenced by other spectroscopic and X-ray data [1].

The Behavior of Active Centers in a Laser Host. A Crystal Field Investigation on Dy3+ in LaF3 Single Crystal

AbstractThe analysis of the observed absorption spectra of Dy3+ ion in the widely used laser host LaF3 is improved upon for D3h site symmetry and the magnetic thermal and hyperfine properties of this system are investigated using the crystal field parameters obtained. Except for one excited state, the fit to all the observed Stark states of the ground multiplet is quite good. The results of the study are discussed in the light of available experimental information.

Radiofrequency spectroscopy of DCCD: Deuterium quadrupole coupling in acetylene

Molecular beam electric resonance spectroscopy has been used to observe the P(16) e and P(16) f transitions in the ν 5- ν 4 band of dideutero acetylene. Hyperfine transitions were resolved in the P(16) e case, providing deuterium quadrupole coupling and spin rotation information. The hyperfine properties are essentially the same for ν 4, J = 16 and ν 5, J = 15 with eQq = 209(1) kHz and C = −0.42(2) kHz. This information is compared with other measurements of deuterium quadrupole coupling in acetylene.

Radio frequency spectra of chloroacetylene in v=0 and v=1 of the C–H stretching vibration

Radio frequency spectroscopy has been carried out on molecular beams of chloroacetylene to yield Stark and chlorine hyperfine properties for the ground and excited C–H stretching vibrational states. For HCC35Cl v=0, μ=0.440 079(1) D, eQq=−79 733.59(4) kHz, and CCl=1.412(4) kHz. For HCC35Cl v=1, μ=0.462 792(1) D, eQq=−79 744.59(5) kHz, and CCl=1.398(3) kHz. For HCC37Cl v=0, μ=0.439 954(1) D, eQq=−62 839.68(9) kHz, and CCl=1.142(6) kHz. For HCC37Cl v=1, μ=0.462 778(1) D, eQq=−62 848.64(10) kHz, and CCl=1.127(8) kHz. The above results are for J=1 levels, while J=1 and J=2 Stark data for the ground state were combined to give an electric polarizability anisotropy, α∥–α⊥=3.87(2) Å3.