HFS Lines Research Articles

EPR study of the hydrogen center in HPHT diamonds grown in carbonate medium

An electron paramagnetic resonance (EPR) study of synthetic diamond crystals grown at HTHP conditions in the carbonate medium Na2CO3CO2H2OC has revealed a hydrogen‐containing center (VOH) along with centers OX1, OX2, and OX3 tentatively associated with oxygen. In the X‐band EPR spectra, the forbidden transitions of the center are superimposed on the allowed HFS lines of one hydrogen atom. We have succeeded in analysis of the allowed transitions in Q‐band experiments. On the basis of the obtained experimental data a hypothetical model of the center has been proposed as a vacancy–oxygen complex with incorporated hydrogen atom. The occurrence of hydrogen in the studied diamond crystals is supported by the presence of CH vibrations in the IR spectra in the range of 3000 cm−1.

CHEMISTRY OF THE SAGITTARIUS DWARF GALAXY: A TOP-LIGHT INITIAL MASS FUNCTION, OUTFLOWS, AND THER-PROCESS

From chemical abundance analysis of stars in the Sagittarius dwarf spheroidal galaxy (Sgr), we conclude that the alpha-element deficiencies cannot be due to the Type Ia supernova (SNIa) time-delay scenario of Tinsley (1979). Instead, the evidence points to low [alpha/Fe] ratios resulting from an initial mass function (IMF) deficient in the highest mass stars. The critical evidence is the 0.4 dex deficiency of [O/Fe], [Mg/Fe] and other hydrostatic elements, contrasting with the normal trend of r-process [Eu/Fe]r with [Fe/H]. Supporting evidence comes from the hydrostatic element (O, Mg, Na, Al, Cu) [X/Fe] ratios, which are inconsistent with iron added to the Milky Way (MW) disk trends. Also, the ratio of hydrostatic to explosive (Si, Ca, Ti) element abundances suggests a relatively top-light IMF. Abundance similarities with the LMC, Fornax and IC 1613, suggest that their alpha-element deficiencies also resulted from IMFs lacking the most massive SNII. For such a top-light IMF, the normal trend of r-process [Eu/Fe]r with [Fe/H], as seen in Sgr, indicates that massive Type II supernovae (>30Msun) cannot be major sources of r-process elements. High [La/Y] ratios, consistent with leaky-box chemical evolution, are confirmed but ~0.3 dex larger than theoretical AGB predictions. This may be due to the 13C pocket mass, or a difference between MW and Sgr AGB stars. Sgr has the lowest [Rb/Zr] ratios known, consistent with low-mass (~2Msun) AGB stars near [Fe/H]=-0.6, likely resulting from leaky-box chemical evolution. The [Cu/O] trend in Sgr and the MW suggest that Cu yields increase with both metallicity and stellar mass, as expected from Cu production by the weak s-process in massive stars. Finally, we present an updated hfs line list, an abundance analysis of Arcturus, and further develop our error analysis formalism.

Reasons for the line broadening in the epr spectra of copper ions in Li2-2x Zn2+x (MoO4)3 lithium-zinc molybdate crystals

An EPR study of Li2−2xZn2+x(MoO4)3 crystals activated by copper ions shows that they occupy the M2 site, one of the three possible sites of both lithium and zinc. In the EPR spectra of Cu2+ copper a broadening of HFS lines and a nonequidistant splitting between them, which are unusual for the orientation H‖gzz, Azz, are observed. In this work possible reasons for such a broadening of HFS lines from copper ions are analyzed: a distortion of the oxygen octahedron due to the introduction of copper ions, second order perturbation theory corrections, superposition of HFS from 63Cu and 65Cu isotopes, and the effect of the charge redistribution in the oxygen octahedron because the cation vacancy providing charge compensation can be located at different distances from the copper ion. It is shown that the first three reasons do not explain the features observed in the EPR spectra. In the case of cation vacancies located in the M3 site and remote at different distances from the copper ion, the charge redistribution in the oxygen octahedron of copper should occur along with the dispersion of HFS parameters and the g-factor. The studies performed in X and Q bands confirm this assumption. The width of HFS lines from copper ions in the EPR spectra measured in the Q band is three times more compared to that measured in the X band.

Ligandenaustauschreaktionen an Kupfer(II)‐Komplexen mit Harnstoffliganden: Synthesen, Strukturen, EPR‐Spektroskopie

AbstractThe synthesis of copper(II) and nickel(II) complexes of N,N‐diethyl‐N'‐benzoylurea HL1, N,N‐diethyl‐N'‐(2, 6‐difluorbenzoyl)urea HL2, N,N‐diethyl‐N'‐benzoylthiourea HL3, N,N‐diethyl‐N'‐(3, 4, 5‐trimethoxybenzoyl)thiourea HL4 and N,N‐diethyl‐N'‐benzimidoylthiourea H2L5 and the crystal structures of HL2, [Cu(L2)2] and [Ni(HL5)2] are reported. All CuII complexes were investigated by EPR spectroscopy in liquid and frozen solutions. The CuII complex [Cu(HL5)2] was additionally studied as diamagnetically diluted powder system [Ni(HL5)2] / [Cu(HL5)2] (99:1). The calculation of electron spin‐density distribution in the first coordination sphere of [Cu(HL5)2] is represented, based on well‐resolved 63, 65Cu and 14N hyperfine structure (hfs) couplings. Ligand exchange reactions of CuII complexes of urea type ligands HL1–4 and H2L5 were studied by means of EPR spectroscopy in liquid solutions. Statistical and quantitative runs were derived from concentration‐dependent hfs line intensities.

SOFIA observations of far-infrared hydroxyl emission toward classical ultracompact HII/OH maser regions

The hydroxyl radical (OH) is found in various environments within the interstellar medium (ISM) of the Milky Way and external galaxies, mostly either in diffuse interstellar clouds or in the warm, dense environments of newly formed low-mass and high-mass stars, i.e, in the dense shells of compact and ultracompact HII regions (UCHIIRs). Until today, most studies of interstellar OH involved the molecule's radio wavelength hyperfine structure (hfs) transitions. These lines are generally not in LTE and either masing or over-cooling complicates their interpretation. In the past, observations of transitions between different rotational levels of OH, which are at far-infrared wavelengths, have suffered from limited spectral and angular resolution. Since these lines have critical densities many orders of magnitude higher than the radio wavelength ground state hfs lines and are emitted from levels with more than 100 K above the ground state, when observed in emission, they probe very dense and warm material. We probe the warm and dense molecular material surrounding the UCHIIR/OH maser sources W3(OH), G10.62-0.39 and NGC 7538 IRS1 by studying the $^2\Pi_{{1/2}}, J = {3/2} - {1/2}$ rotational transition of OH in emission and, toward the last source also the molecule's $^2\Pi_{3/2}, J = 5/2 - 3/2$ ground-state transition in absorption. We used the Stratospheric Observatory for Infrared Astronomy (SOFIA) to observe these OH lines, which are near 1.84 THz ($163 \mu$m) and 2.51 THz ($119.3 \mu$m). We clearly detect the OH lines, some of which are blended with each other. Employing non-LTE radiative transfer calculations we predict line intensities using models of a low OH abundance envelope versus a compact, high-abundance source corresponding to the origin of the radio OH lines.

Structure and EPR spectra of binuclear copper(II) complexes with acyldihydrazones of benzenedicarboxylic acids and trifluoroacetylacetone

Binuclear copper(II) complexes with acyldihydrazones of benzenedicarboxylic acid and trifluoroacetylacetone have been synthesized and studied. The structure of the copper(II) complex with diacylhydrazone of 1,3-benzenedicarboxylic acid (H4L) of composition [Cu2L · 2LPy] has been studied by X-ray diffraction. The crystals are triclinic: a = 9.2298(4) A, b = 11.8510(6) A, c = 13.8314(7) A, α = 90.780(3)°, β = 96.124(3)°, γ = 99.264(3)°, space group \(P\bar 1\), Z = 2. The number of symmetry-unrelated reflections with I > 2σ(I) 5941; R = 0.0357, Rw = 0.0589. The complex contains two equivalent copper atoms at a distance of 9.56 A from each other in the square-planar coordination environment. The high-temperature EPR spectra of the complexes show a signal of seven HFS lines indicating the coupling of unpaired electrons to two equivalent copper nuclei (g = 2.113−2.116, aCu = 37.0−37.2 × 10−4 cm−1).

Copper(II) complex with salicylaldehyde N-(2-salicylideneiminoglutaryl)hydrazone: Synthesis and structure

A copper(II) complex with salicylaldehyde N-(2-salicylideneiminoglutaryl)hydrazone (H4L) of the formula [Cu2L · 2Py]2 · 8H2O (I) was obtained and characterized by X-ray diffraction. The crystals are monoclinic, space group P21, a = 13.0663 A, b = 16.5553 A, c = 17.7650 A, β = 97.9420°; Z = 4. The complex is tetranuclear with a “dimer-of-dimers” structure in which the copper cations of two binuclear subunits are linked by phenoxy bridges. The EPR spectra of solutions of complex I show a superposition of two signals of four HFS lines (g 1 = 2.111, a 1 = 56.8 × 10−4 cm−1 and g 2 = 2.183, a 2 = 71.0 × 10−4 cm−1).

Binuclear copper(II) complexes with acyldihydrazones of N-benzenesulfonyl-L-aspartic acid

The structure and the EPR spectra of copper(II) coordination compounds with acyldihydrazones of N-benzenesulfonyl-L-aspartic acid and salicylaldehyde (2-hydroxyacetophenone) were described. The compounds were studied by chemical and thermal analyses, IR spectroscopy, and EPR. The molecular and crystal structures of copper(II) complexes with N-benzenesulfonyl-L-aspartic acid bis(salicylidene)hydrazone (H4L1) [Cu2L1 · 2Py] · 1.5 H2O was determined by X-ray diffraction. The crystals are triclinic: a = 10.4714(4) A, b = 12.9702(5) A, c = 14.6187(9) A, α = 104.763(2)°, β = 93.082(2)°, γ = 111.4240(10)°, space group P \(\bar 1\), Z = 2. The binuclear complexes containing copper cations whose coordination polyhedra are connected by an aliphatic spacer (Cu...Cu, 8.669 A) are additionally linked by phenoxy bridges (Cu...Cu, 3.398 A). The EPR spectra of these compounds in solutions exhibit an isotropic signal of seven HFS lines due to two equivalent copper ions with the spin Hamiltonian parameters g = 2.115−2.120, a Cu = (35.5−38.0) × 10−4 cm−1, which is indicative of weak exchange interactions between the paramagnetic sites.

Spacer-armed binuclear copper(ii) complexes with salicylidene hydrazones of N-benzoylaminodicarboxylic acids

The structure and EPR spectra of copper(II) complexes with bis(salicylidene)hydrozones of N-benzoyl-L-aspartic and N-benzoyl-L-glutamic acids have been described. The compounds have been studied by chemical and thermal analyses, IR spectroscopy, and EPR spectroscopy. The molecular and crystal structure of the copper(II) complex with bis(salicylidene)hydrozone of N-benzoyl-L-aspartic acid (H4L) of composition [Cu2L · 2Py] · 2CH3OH · H2O has been determined by X-ray single-crystal diffraction. The crystals are monoclinic: a = 10.3316(7) A, b = 16.7552(9) A,c = 11.0137(6) A, β = 105.758(3)°, space group P21, Z = 2. The complex has a polymeric structure composed of alternating copper-containing binuclear fragments bound to each other either via phenoxy bridges or via an aliphatic spacer (the Cu…Cu distances are 3.471 A and 8.939 A, respectively). The EPR spectra of the solutions of the complexes under study shows an isotropic signal comprising seven HFS lines due to two equivalent copper nuclei with the spin Hamiltonian parameters g = 2.115–2.122 and aCu = (36.1–36.9) × 10−4 cm−1, which indicates the reaization of weak exchange coupling of the paramagnetic centers.

Binuclear copper(II) complexes with acyldihydrazones of 1,4-cyclohexanedicarboxylic acid

The binuclear copper(II) complexes with acyldihydrazones formed by 1,4-cyclohexanedicarboxylic acid and salicylaldehyde or 2-hydroxyacetophenone were synthesized and studied. The structure of the complex with 1,4-cyclohexanedicarboxylic acid bis(salicylidene)hydrazone (H4L1) [Cu2L1(Py)2] was studied by X-ray diffraction. The crystals are triclinic: a = 8.1852(4) A, b = 8.5157(5) A, c = 11.6553(7) A, α = 80.678(3)°, β = 70.041(4)°, γ = 74.803(3)°. Space group \(P\bar 1\), Z = 1. The number of symmetrically independent reflections with I > 2(σ(I)) is 2245, R = 0.0395; Rw = 0.0917. The complex contains two equivalent copper atoms located at a 10.772 A distance from each other. The coordination polyhedra have a square geometry and are involved in the intermolecular π/π-stacking. The EPR spectra of solutions of the binuclear complexes show an isotropic signal of seven HFS lines (g = 2.113–2.118, ACu ≈ 38 G), indicating interaction between the unpaired electrons and the two equivalent copper nuclei. The possible exchange interaction channels were analyzed.

EPR study of RLi 2O.V 2O 5, RNa 2O.V 2O 5, RCaO.V 2O 5, and RBaO.V 2O 5 modified vanadate glass systems

Experimental EPR spectra in several modified vanadate glass systems reveal hyperfine structure (hfs) lines whose widths vary with the molar ratio of modifier to vanadium pentoxide, R. In the RNa 2O.V 2O 5 system, for example, hfs lines show no resolution at low R values (near 0.1); by contrast, these lines exhibit dramatic narrowing as R approaches 0.5. In the model proposed here, this narrowing is due to an increase in hopping time for small polarons associated with V 4+ ions in these systems. Increases in polaron hopping times are accompanied by increases in electron spin-spin relaxation times T 2's, and, an associated narrowing of EPR linewidths. Experiments confirm that spectral widths are limited by electron T 2's due to the fact that EPR linewidths do not vary with temperature down to 4.2 K. Resolved spectra in RNa 2O.V 2O 5 at R = 0.5 reveal a hyperfine coupling parameter of 0.0177 ± 0.0008 T, corresponding to an upper-limit polaron hopping frequency of 487 ± 20 MHz. By similar analyses, the systems of RCaO.V 2O 5, RBaO.V 2O 5, and RLi 2O.V 2O 5 exhibit comparable polaron hopping frequencies limits of 480 ± 20 MHz, 469 ± 20 MHz, and 468 ± 20 MHz, respectively, when R is near 1.0. In addition to the relaxation effects discussed here, results of modeling of resolved spectra to obtain hyperfine coupling constants A || and A ┴, and g ┴ values g || and g ┴ are presented and discussed.

Structure and EPR spectra of binuclear copper(II) complexes with acyldihydrazones of benzenedicarboxylic acids and 5-substituted 2-hydroxyacetophenones

Binuclear copper(II) complexes with acyldihydrazones of 1,3- or 1,4 benzenedicarboxylic acid and 5-methyl- or 5-bromo-2-hydroxyacetophenone in which coordination polyhedra are connected by an aromatic bridge have been synthesized and studied. The structure of the copper(II) complex with diacylhydrazone of isophthalic acid and 2-hydroxy-5-methylacetophenone (H4L) of composition [Cu2L · 3Py] was studied by X-ray diffraction. The crystals are monoclinic: a = 12.1996(12) A, b = 17.7295(17) A, c = 17.9339(17) A, β = 109.7450(10)°, space group P21/n, Z = 4. The complex is of the “dimer of dimers” type and contains two binuclear subunits that bind together into a centrosymmetric dimer owing to the coordination of the copper cation to the phenoxyl oxygen atom of a neighboring binuclear molecule to form the Cu2O2 moiety, in which the copper atoms are 3.409 A apart. The distance between the copper(II) cations in the binuclear subunit is 8.56 atoms (2N + O) of the doubly deprotonated acylhydrazone moiety and the nitrogen atom of the pyridine molecule. One of the copper cation is additionally coordinated to an extra pyridine molecule so that its coordination sphere is completed to a tetragonal pyramid. The second copper atom is involved in additional interaction with the phenoxyl oxygen atom of the neighboring molecule. The EPR spectra of solutions of the binuclear complexes show an isotropic signal of four HFS lines (g o = 2.065–2.143, a Cu = 52.1–66.5 × 10−4 cm−1) typical of mononuclear copper(II) complexes.

Binuclear copper(II) complexes with acyldihydrazones of 4-formyl-5-hydroxy-3-methyl-1-phenylpyrazoles

The synthesis of copper(II) binuclear complexes with acyldihydrazones of saturated carboxylic acids and 4-formyl-5-hydroxy-3-methyl-1-phenylpyrazoles in which the coordination polyhedra are connected by polymethylene chains of different length (two to five units) is described. The complexes were studied by chemical and thermal analysis, IR spectroscopy, and EPR. The molecular and crystal structure of the copper(II) complex with glutaric acid and 1-(4′-chlorophenyl)-4-formyl-5-hydroxy-3-methylpyrazole acyldihydrazone (H4L) described as [Cu2L·2Py] · Py · 4H2O was determined by X-ray diffraction. The crystals are orthorhombic: a = 24.789(7) A, b = 39.319(9) A, c = 4.6336(14) A, space group Pnma, Z = 4. The number of symmetrically unrelated reflections is 4716, R = 0.0606, Rw = 0.1307. The central atoms are separated by a chain of eight σ bonds and are located at a distance of 8.939 A. The copper coordination polyhedron is a square. A specific feature of the crystal structure is the stacking interaction involving chelate rings and the pyrazole ring, resulting in stacks of molecular complexes. The EPR spectrum of a solution of the complex based on the acyldihydrazone of succinic acid and 4-formyl-5-hydroxy-3-methyl-1-phenylpyrazole recorded at room temperature exhibits seven HFS lines with an intensity ratio of 1: 2: 3: 4: 3: 2: 1 and a constant of 33.3 G as a result of exchange coupling of the unpaired electrons to the two equivalent copper nuclei. An increase in the length of the polymethylene chain to 3–5 units or introduction of the para-chlorine atom into the benzene ring hampers the exchange interactions, and the EPR spectrum shows a signal of four HFS lines with a constant of 55–70 G typical of monomeric copper(II) complexes.

Possibility of measuring the amount of intergalactic metals with 14N VII HFS line

AbstractWe discuss possibility of observations of the warm-hot intergalactic medium using the hyperfine structure line of highly charged nitrogen ion 14N VII (rest wavelength λ = 5.652 mm). Observations of this line will allow to separate bulk and turbulent motions in the observed target and will broaden the information about the gas ionization state, chemical and isotopic composition.Wavelength of this line is well-suited for ground-based observation of objects at z ≈ 0.15 − 0.6 when it is redshifted to the widely-used 6.5 − 9 mm spectral band, and, for example, for z ≥ 1.3, when the line can be observed in 1.3 cm band and at lower frequencies.

Binuclear copper(II) complexes with acyldihydrazones of saturated carboxylic acids and pyruvic acid

Copper(II) binuclear complexes with acyldihydrazones of saturated carboxylic acids and pyruvic acid in which the coordination polyhedra are connected by polymethylene chains of different length (1 to 5 units) were synthesized and studied by chemical and thermogravimetric analysis, IR spectroscopy, and EPR. The structure of binuclear copper(II) complex with succinic acid acyldihydrazone [Cu2L · 4Py] · 2Py was determined by X-ray diffraction. The crystals are monoclinic: a = 14.3795(6), b = 8.8736(4), c = 15.9147(7) A, β = 101.062(3)°, space group P21/c, Z = 2. The number of independent reflections with I > 2σ(I) = 2804, R = 0.042, Rw = 0.087. The copper atoms are spaced by a chain of seven σ bonds at 8.922 A. The coordination polyhedron can be described as a tetragonal pyramid highly distorted toward a trigonal bipyramid. The EPR spectra of solutions of complexes based on malonic, succinic, glutaric, and adipinic acids exhibit a poorly resolved signal of seven HFS lines with a constant of (26.3–27.0) × 10−4 cm−1, which attests to the presence of weak exchange interactions between paramagnetic centers. An increase in the length of the polymethylene spaur suppresses exchange interactions, and the EPR spectrum of the complex based on pimelic acid acyldihydrazone shows a signal of four HFS lines with a constant of 43.8 × 10−4 cm−1 typical of monomeric copper(II) complexes.

Asymmetry of hyperfine-structure components of the 5 1S0-53P1 113Cd line perturbed by argon

Experimental results of a systematic study of profiles of the hyperfine-structure components of the intercombination 51S0 – 5 3P1 line of the even-odd 113Cd isotope perturbed by argon performed by means of a laser-induced fluorescence method are reported. We have found that the values of total line asymmetries of both hfs line components are different.

Pressure broadening of hyperfine-structure components of the 5 1S0– 5 3P1 113Cd line perturbed by argon

Experimental results of a spectroscopic study of argon broadened profiles of the hyperfine-structure components of the intercombination 326.1 nm line 113 Cd isotope are reported. We have found that the values of Lorentzian (collisional) widths of both hfs line components are different.

ESR spectra of spacered copper(II) dimers of 5-bromo-2-hydroxyacetophenone acyldihydrazones based on aliphatic dicarboxylic acids

Binuclear copper(II) complexes with 5-bromo-2-hydroxyacetophenone acyldihydrazones (H4L) with the composition [Cu2L·nPy] where the coordination polyhedra are linked by polymethylene chains with different lengths (from one to five units) have been synthesized and studied. The ESR spectrum of a polycrystalline sample of a complex based on malonyldihydrazone contains a major signal (g = 2.11) together with a weak signal corresponding to the forbidden transition (ΔMS = 2, g = 4.18). At room temperature, ESR spectra of solutions of complexes of acyldihydrazones based on malonic, succinic, glutaric, and adipic acids contain seven HFS lines from two equivalent copper nuclei. These lines result from weak spin-spin exchange interaction between two unpaired electrons with the constant (36–38)·10−4 cm−1. An increase in the polymethylene chain length to five units prevents the exchange interactions, and the ESR spectrum of a complex of the acyldihydrazone based on pimelic acid contains a signal of four HFS lines (aCu = 69.5·10−4 cm−1), which is common to the monomeric copper(II) compounds. In the parallel orientation, the ESR spectrum of a frozen solution of the complex of malonyldihydrazone contained the superposition of signals due to fine and hyperfine structures with similar constants (D∥ = 0.0074 cm−1, A∥ = 0.0070 cm−1, g∥ = 2.089, g⊥ = 2.053).

Molecular structures and ESR spectra of copper(ii) complexes with 2-hydroxypropiophenone acyldihydrazones

The dinuclear copper(ii) complexes with 2-hydroxypropiophenone acyldihydrazones (H4L) having the composition [Cu2L·mPy], where the L ligand contains the polymethylene chain with different lengths (from two to five units), were synthesized and studied. The crystal and molecular structures of the 2-hydroxypropiophenone adipoylhydrazone complex [Cu2L·4Py]·Py were established by X-ray diffraction analysis. Copper atoms are 8.212 A distant from each other, and their nearest environment has the tetragonal pyramidal geometry. The ESR spectra of solutions of the complexes based on acyldihydrazones of succinic, glutaric, and adipic acids contain seven HFS lines with the constant ∼40·10–4 cm–1 from two equivalent copper atoms. The spectra were interpreted as a result of the spin-spin exchange interaction of two unpaired electrons. An increase in the polymethylene chain length to five units prevents exchange interactions. The ESR spectrum of the complex with acyldihydrazone of pimelic acid contains a signal of four HFS lines with aCu = 73.4·10–4 cm–1, which is typical of mononuclear copper(ii) complexes.

ESR spectra of copper(ii) complexes with 2-hydroxy-5-methyl- and 5-chloro-2-hydroxyacetophenone acyldihydrazones

ESR spectra of binuclear copper(ii) complexes with 2-hydroxy-5-methyl- and 5-chloro-2-hydroxyacetophenone acyldihydrazones (H4L) [Cu2L·2Py], in which the coordination polyhedra are linked by the polymethylene chain with different lengths (from one to five units), were studied. The spectra of the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids exhibit weak exchange interactions between the paramagnetic sites. These interactions induce seven HFS lines from two equivalent copper nuclei with the constant ∼40·10–4 cm–1 in the ESR spectra of liquid solutions. An increase in the polymethylene chain length to five units prevents the exchange interactions, and the ESR spectrum of the complex based on heptadioic acyldihydrazone contains the signal of four HFS lines with the constant ∼72·10–4 cm–1, which is common for the copper(ii) monomeric compounds.