10Dq Values Research Articles

Transparent and radiation shielding effective Na2O–CrO3 borate glasses via AgI additives

The current paper investigates the impact of silver iodide (AgI) on the structure, optical, and radiation shielding parameters of borate glasses embedded with low amounts of CrO3, high levels of Na2O, and various quantities of AgI (from 1 to 5 mol%). These glasses (named BNaCrAg-glasses) were synthesized and their properties were investigated. Fourier transform infrared (FTIR) analyses of BNaCrAg-glasses demonstrated that the ratio of BO4/BO3 units increased with increasing AgI. The existence of Cr cations, with their Cr6+ state, was recognized from the absorption bands at 384–392 nm and 334–338 nm. Furthermore, the absorption bands at 580–589 nm at 409–440 nm through the visible region confirmed the existence of Cr-ions as Cr3+ in the octahedral symmetry. The crystal field splitting (10Dq) was calculated from the 580–589 nm bands. The values of 10Dq decreased with AgI doping due to replacing oxygen with iodide anions. The transmittance at 700 nm increased from 24 to 80%, while AgI addition increased from 0 to 5 mol%. The glass sample with the highest AgI content had the lowest half-value layer and maximum linear attenuation coefficient. Thus, the new BNaCrAg-glasses combine good transparency with good attenuation of low energy radiation and can be used to protect the radiation workers. Furthermore, these glasses offer high-energy optical transitions suitable for UV optics, such as ultraviolet digital photography and insect light traps.

Impact of Y2O3 on the structural, optical, radiation shielding, and ligand field parameters of transparent borate glass containing constant CrO3 and high Na2O contents

This study aims to investigate the impact of the rare earth element yttrium on the optical properties of chromium (Cr)-doped borate glasses. A series of borate glasses (labeled as BNaCrY glasses) were prepared and studied, each with a constant amount of chromium trioxide (CrO3) but doped with varying amounts of yttrium oxide (Y2O3). Infrared analysis revealed four distinct spectral areas in the internal structure of all BNaCrY glasses. Optical absorption spectra were used to investigate the impact of Y2O3 doping on the optical transitions of BNaCrY glasses. The presence of Cr cations caused the appearance of an absorption band at 379–383 nm, which overlapped with the Urbach edge that is commonly given an edge-like at 430 nm. The Urbach edge has been manifested through a full deconvolution attempt. Cr cations in the Cr3+ state were confirmed by visible absorption bands and are nestled in the octahedral positions. The band at 574–593 nm was used to determine the crystal field splitting (10Dq) for all BNaCrY glasses. Due to the increased number of O anions around the Cr cation, the values of 10Dq increased with Y2O3 doping. The remarkable increase in 10Dq was attributed to increased interaction between Cr cations and their surroundings. In contrast, the shielding parameters were taken into account when evaluating the ability of these transparent glasses to protect against nuclear radiation. We found that the sample with the highest Y2O3 concentration had the highest linear attenuation coefficient and the lowest half-value layer. Thus, BNaCrY glasses are more efficient as attenuators than commercial glasses (such as the Rider and Osmania glasses), especially at low photon energies.

Impact of Cr3+ substitution on the nephelauxetic ratio and Racah parameter of Cr-Mn-Zn nanoferrites

For the first time, we present the ligand field splitting (10Dq) nephelauxetic ratio (β), Racah parameter (B) and stability of Cr3+ within Mn–Zn nanoferrite which synthesized using the citrate route. These parameters were determined via optical absorption spectra. The obtained bands in the significance range of optical absorption spectra are wide as well as asymmetric; therefore the deconvolution process becomes a necessary task. The values of 10Dq and B have been estimated from the produced bands. The values of 10Dq are observed to increase from 16366.61 to 16447.37 cm−1 whereas, B values are observed to decrease from 829.81 to 760.80 cm−1 with additional Cr3+ substitution. The increasing 10Dq and decreasing B values, evidence for bonds between Cr3+ ions with their environments became a further covalent (less ionic). Moreover, the values of β are observed to decrease for further Cr3+ substitution. This decrease of β produces less stability between Cr3+ and its ligand. Furthermore, Dq/B values declare that Cr3+ centers are in the low-field sites by a slight tendency towards the high-field sites with further Cr/Fe substitution process. Therefore, it was suggested that Cr3+ substituted Mn–Zn nanoferrites are excellent candidates for diverse optical applications such as a tunable laser.

Study on the molecular orbital energies of ruby under pressure

We calculated the molecular orbital (MO) energies of α-Al2O3: Cr3+ (ruby) under pressure non-empirically based on one-electron calculations. The pressure was applied to the samples from ca. 0–110 GPa. Two different approaches to estimate the effect of lattice relaxation are Shannon's crystal radii method and the geometry optimization using CASTEP software. The one-electron calculations were used to estimate the MO energies, which were performed using the Discrete Variational Xα (DV-Xα) software. We found that the splitting of the crystal field (10Dq) increased as the applied pressure grew. We pointed out that collectively considering the effect of lattice relaxation and using the more substantial cluster size has a significant effect on the value of 10Dq.

Spectroscopic and magnetic properties of three M(PO3)3 (M=Cr and Mo) metaphosphates

Three metaphosphates with formula M(PO3)3 (M=Cr and Mo) and Cr2(P6O18) have been synthesized and characterized. IR data allow establishment of a good correlation between the vibrational frequencies and the chain or ring structures of the M(PO3)3 (M=Cr, Mo) metaphosphates and the Cr2(P6O18) hexametaphosphate, respectively. The reflectance diffuse spectra show bands belonging to the CrIII and MoIII cations in octahedral symmetry. The values of 10Dq and Racah parameters B and C have been calculated. The percentage of reduction calculated for the B parameter (≈70%) is indicative of a significant degree of covalence in the M–O (M=Cr, Mo) bonds. The EPR spectra of the metaphosphate compounds have been explained on the basis of the existence of more than one different environment for the metallic cations. In doped aluminium metaphosphates with CrIII and MoIII ions the EPR data indicate the presence of one centre with |D|>hν and two centres with |D|<hν. Magnetic measurements show an antiferromagnetic behaviour for all compounds. In the case of the Cr2(P6O18) hexametaphosphate the existence of a weak ferromagnetism intrinsic to the sample has been observed at ca. 3 K.

Electronic structure of tetrahedral iron(III)—sulfur clusters in alkaline thioferrates: an X-ray absorption study

X-ray absorption spectra of Na 5FeS 4 and KFeS 2 containing separate and interconnected edge-shared FeS 4 5− tetrahedra, respectively, are reported and interpreted in terms of an S = 5/2 ground state for Fe 3+ in both compounds. A rather small value of the ligand-to-metal charge transfer energy Δ eff was indicated by the comparison of the experimental Fe 2 p XAS spectrum with atomic multiplet calculations, reflecting an almost 1 : 1 admixture of d 5 and d 6 L ( L hole on the ligand) character in the ground state for Na 5FeS 4. The broadening of the main peak toward higher energies when going from Na 5FeS 4 to KFeS 2 is attributed to symmetry lowering from T d to D 2 d . Ligand-field parameterization schemes, such as the angular overlap model, are found to be quantitatively not applicable for the systems under consideration. The phase diagram of d 5 ions and its dependence on the crystal-field splitting (10Dq) and the ligand-to-metal charge transfer energy (Δ eff) are discussed and it is shown that an intermediate spin state ( S = 3/2) can become stable for negative Δ eff and moderate values of 10Dq and metal—ligand hybridization. This presents another limit for the ligand-field approach and the Tanabe—Sugano diagrams, where only S = 5/2 and S = 1/2 ground states are predicted. For the Fe 3+ in a tetrahedral field the theory indicates that it is unlikely that the S = 3/2 and S = 1/2 states become the ground state since the gain in energy due to ligand—ligand coupling and the relatively small charge transfer energy (both tending to lower energetically the S = 3/2 state) are not sufficient to overcome the high exchange stabilization of the high-spin ( S = 5/2) state.

High-resolution parallel electron energy-loss spectroscopy of Mn L2,3-edges in inorganic manganese compounds

Parallel electron energy-loss spectroscopy (PEELS) in a scanning transmission electron microscope (STEM) was used to record the Mn L2,3-edges from a range of natural and synthetic manganese containing materials, covering valences 0, II, III, IV and VII, with an energy resolution of ca. 0.5 eV. The Mn L2,3 electron-loss near-edge structure (ELNES) of these edges provided a sensitive fingerprint of its valence. The Mn2+ L2,3-edges show little sensitivity to the local site symmetry of the ligands surrounding the manganese. This is illustrated by comparing the Mn L2,3-edges from 4-, 6- and 8-fold coordinated Mn2+. In contrast, the Mn L3-edges from Mn3+ and Mn4+ containing minerals exhibited ELNES that are interpreted in terms of a crystal-field splitting of the 3d electrons, governed by the symmetry of the surrounding ligands. The Mn L3-edges for octahedrally coordinated Mn2+, Mn3+ and Mn4+ showed variations in their ELNES that were sensitive to the crystal-field strength. The crystal-field strength (10Dq) was measured from these edges and compared very well with published optically determined values. The magnitude of 10Dq measured from the Mn L3-edges and their O K-edge prepeaks of the manganese oxides were almost identical. This further confirms that the value of 10Dq measured at the Mn L3-edge is correct. Selected spectra are compared with theoretical 2p atomic multiplet spectra and the differences and similarities are explained in terms of the covalency and site symmetry of the manganese. The Mn L3-edges allow the valence of the manganese to be ascertained, even in multivalent state materials, and can also be used to determine 10Dq.

Transition Metal Complexes of 2-(N-Succinimidyl)Pyrimidine

Abstract 2-(N-succinimidyl) pyrimidine complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Hg(II), Ru(III) and Pd(II) have been prepared and characterized by elemental analyses, IR, UV-Vis spectra and magnetic moment measurements. High melting points and non-solubility in common organic solvents indicate their polymeric nature. The Ru(III), Pd(II) and Cu(II) complexes are soluble in DMSO. The low molar conductance of these complexes indicates their non-electrolytic nature. The observed magnetic moment values of the complexes are very close to those calculated for the metal in an octahedral environment of ligands. The values of 10Dq, B and have also been determined in cases where possible.

Luminescence from Ti2+ ions in LiF crystals

Luminescence of Ti2+: LiF crystals in the wavelength range 650–900 nm excited using laser radiation is reported. The values of 10Dq and the Racah B parameter obtained from the present results indicate that in LiF the 1E, 1T2, and 3T2 energy levels are almost at the “cross-over” point in the Tanabe-Sugano diagram. In consequence photoluminescence from all three energy levels to the ground state is observed. At low temperature (T ∼ 14 K) the emission is mainly due to sharp emission lines with weak vibronic structure due to the 1E, 1T2→3T1 transitions of Ti2+ ions. The 3T2→3T1 broad-band emission is weak at low temperature, becoming stronger at 300 K due to a phonon-assisted tunnelling process, similar to that observed in Cr3+: garnets [1]. The excitation spectrum of these lines is a broad peak at 590 nm due to absorption in the 3T1→3T2 transition.

X ? studies of laser crystals

This paper reports the spin-polarized self-consistent-charge discrete variational (SCC-DV-Xα) calculations for the garnets GGG(Ca, Mg, Zr), GGG, YGG and YAG. The calculated values of 10Dq for these garnets are reported for the first time, and are in good agreement with the experimental values. The relation between the calculated values and the distances of the central ion and the ligand ions is discussed. The energy values of the doublet state2Eg were also obtained, and the reason why YAG:Cr3+ only emits sharp fluorescence whereas GGG(Ca, Mg, Zr):Cr3+ can also emit strong broad fluorescence are explained.

AnX ? study of the laser crystal MgF2:V2+

The electronic structures of the laser crystal MgF2:V2+ were obtained with the spinpolarized MS-Xα method. The calculated value of 10Dq and the energies of the lowest doublet states were given for the first time. The relations between the laser properties and the electronic structures were discussed.

Optical Absorption Spectra of Ni&lt;sup&gt;2+&lt;/sup&gt; Ions and IR Spectra in (100-&lt;i&gt;x&lt;/i&gt;) (PbO⋅GeO&lt;sub&gt;2&lt;/sub&gt;)⋅&lt;i&gt;x&lt;/i&gt;RO (R=Mg, Ca, Sr, Ba) Glasses

Optical absorption spectra of Ni2+ ion (100-x) (PbO⋅GeO2)⋅xRO⋅0.2wt% NiO glasses are measured, and the results are obtained as follows.The value of 10Dq which represents the intensity of the ligand field shifts toward higher wave number with increasing alkaline earth metal content. The increasing intensity of the ligand field is considered to be the formation of GeO68-, where the glass network was destroyed by alkaline earth metals. In this study, the ν4 peak appears only at 20mol% BaO, which represents a Ni2+ ion with 4-coordination. In other systems the ν4 peak does not appear clearly. It is considered that the Ni2+ ion does not become 4-coordination.According to the measurements of infrared spectra, most of this system consists of Ge6 groups, and the variation of coordination number of Ge with the alkaline earth metal contents hardly appear.

Electronic d-d spectra and ligand-dissociation rates of pentacyanoruthenate(II) ions

The electronic spectra of a series of [Ru(CN)5L]n– complexes (L = H2O, NH3, pyrazine, dimethyl sulphoxide, or CN–) have been measured in aqueous solution. The d-d bands were assigned on the basis of a ligand-field model for tetragonally distorted octahedra and the energy of the transitions, which depends on the nature of L, were found to correlate with the rate constant for the dissociation of L from [Ru (CN)5L]n–, k–L. Comparisons are made with the similar [Fe(CN)5L]n– series. A new value of 10Dq, 4.2 µm–1, is proposed for [Ru(CN)6]4–, which is significantly higher than that corresponding to [Fe(CN)6]4–, as expected from ligand-field theory.

Effects of a partial relaxation of the crystal lattice on the calculation of the electronic structure of CrF3−6 in ‘‘isolated-cluster’’ and ‘‘shared-cluster’’ crystals

The electronic structure of the CrF3−6 in isolated-cluster crystals (K2NaCrF6, Rb2NaCrF6, Rb2KCrF6, and Cs2KCrF6) and in the shared-cluster system CrF3 has been calculated in terms of an open-shell Hartree–Fock–Roothaan SCF methodology which includes the corresponding cluster–lattice interactions. These interactions have been calculated with different models of the crystal lattice. First, a rigid point-charge model has been used to compute the lattice potential. Then, this lattice representation has been partially relaxed in the sense that either the values of the point charges q(Cr), q(F) or the Cr–F internuclear distance or both are allowed to change in order to be consistent with the predictions of the cluster calculation. In CrF3 the relaxation has been limited to the values of the point charges. In the isolated-cluster lattices it is extended to include the lattice value of the Cr–F distance. The results of these calculations have been analyzed with particular attention to the prediction of the equilibrium geometry and the electronic transition 10Dq. The effect of the partial lattice relaxation on these two observables turns out to be rather significative in CrF3 but uniformly small in the isolated-cluster lattices. The values of Re and 10Dq obtained in the best calculation on CrF3 are in very good agreement with the experimental observations.

The excitation spectra of tetrahedral complex compounds of manganese(II) bromide with hydrobromides of some derivatives of pyridine and pyperidine

The excitation spectra of complex compounds of magnanese (II) bromide with hydrobromides of some derivatives of pyridine and pyperidine have been studied at temperatures of 77 and 298 K. The character and arrangement bands of the excitation spectra as well as the green luminescence observed are indicative of tetrahedral structure of these compounds. The mechanism of production of the spectra has been explained in terms of ligand field theory. The Racah parameters calculated and the value of 10Dq was estimated to be about 3100 cm−1. In analyzing the excitation spectra an original method of computation was applied which gave very good results in resolving the bands.

Detailed crossover studies of transition metal ions

The complete ligand field, interelectronic repulsion, and spin-orbit interaction matrices were solved for the octahedral and tetrahedrald4 andd6 electron configurations. The results are employed in a detailed study of the crossover region. It is demonstrated that, close to the crossover, complicated mixing and interaction patterns may arise. A sharp crossover is encountered in the octahedrald6 system exclusively whereΓ1 andΓ5 levels are involved. In all situations where the two ground levels transform according to the same irreducible representation, the crossover is redefined by that value of 10Dq where both ground terms participate in the lowest level to equal amounts.

Aniline complexes of ruthenium(II) and ruthenium(III) halides

The preparations, i.r. and electronic spectra, and magnetic susceptibilities of the ruthenium(III) complexes A[RuX4-(aniline)2](A = Cs, Me4N, C6H5NH3 or C5H6N, and X = Cl, Br, or I); and of the ruthenium(II) complexes [RuL6]Br2 and RuL4Br2(L = a substituted aniline) are reported. From their spectroscopic properties the compounds containing co-ordinated halide are assigned trans-structures. Values of 10Dq obtained from the spectra of [RuL6]Br2 place substituted anilines between ethylenediamine and water in the spectrochemical series. A compound [C6H5NH3]5[Ru3Br14] has been partly characterised.

Vanadium(II) chemistry. Part I. Magnetic and spectroscopic investigations of the sulphate and double sulphates

The simple sulphate VSO4,6H2O has been prepared by electrolytic reduction, and the Tutton salts M2[V(H2O)6](SO4)2(M = NH4, K, Rb, and Cs) have been obtained from it by the addition of the appropriate univalent sulphate. The sulphate is commonly reported as a heptahydrate, but in this investigation only a hexahydrate, which is probably isomorphous with ZnSO4,6H2O, has been obtained. The magnetic moments are a little below the spin-only value (3·87 B.M.) and are invariant with temperature. Electronic reflectance spectra at room temperature and liquid-nitrogen temperatures are consistent with vanadium(II) in Oh symmetry, with values of 10Dq,B, and C of approximately 12,000, 650, and 2600 cm.–1 respectively.

An analysis of the electronic spectra of bis-amine cobalt halides: a novel effect of steric hindrance

The electronic absorption spectra (5000–30,000 cm.–1)(in chloroform) of thirty-three complexes of general formula (Amine)2CoX2 where the amine is quinoline, isoquinoline, 2,6-dimethylpyrazine, pyridine, or a 2-, 3-, or 4-substituted pyridine, and X is Cl, Br, I, NCS, NCO, or NCSe, are reported. The near-infrared absorption band is split into three well defined components, whose overall width is some 1500–2000 cm.–1 greater than is observed in regular tetrahedral cobalt derivatives (such as CoX42–). These three components are assigned to the 4B2â†�4A2, 4A2â†�4A2, and 4B1â†�4A2 transitions in C2v symmetry. With the exception of one band the absorption spectra are virtually independent of the amine throughout the entire region studied. The supposed 4B2â†�4A2 component of the near-infrared absorption decreases in energy by as much as 1000 cm.–1 when the complex contains an α-substituted pyridine. A simple group-theoretical argument consistent with the occurrence of inter-ligand repulsions is suggested to explain this phenomenon. Mean values of 10Dq and B are computed and discussed.

An extended Wolfsberg-Helmholz calculation on CuF6-4

A semi-empirical calculation of the orbital energy levels of CuF6 -4 has been performed using the Wolfsberg-Helmholz approximations as extended by Ballhausen and Gray. The calculated value of 10Dq is rather insensitive to the initial assumptions and is in good agreement with experiments. The location of the ‘non-bonding’ t 1u level is on the other hand found to be very dependent upon the atomic wavefunctions used.