Effect of Ni2+ Doping on the Growth and Properties of Mn-L-Histidine Hydrochloride Monohydrate Crystals

The main focus of this work had been to grow good quality crystals from amino acids and amino acid-based materials for nonlinear optics (NLO) applications. For the first time, a series of amino acid complexes doped with transition metal ions were grown in our laboratory from aqueous solutions by slow evaporation technique. Ni(II) ion doped Manganese L-Histidine hydrochloride monohydrate (Ni(II)-MnLHICl) crystals were grown on the same lines and were characterized by powder X-ray diffraction (XRD), optical absorption, electron paramagnetic resonance, and infrared absorption studies. From Powder XRD, the unit cell lattice parameters were calculated as a=1.5301 nm, b=0.8928 nm and c=0.6851 nm. From electron paramagnetic resonance (EPR) spectra, isotropic “g” factor and spin hamiltonian parameter A all were calculated as 2.0439 and 20×10−4, respectively. From optical absorption studies, crystal field splitting value (Dq) and the interelectron repulsion parameters B and C were calculated for Ni2+ and Mn2+ as Dq=850 cm−1, B=725 cm−1, C=2640 cm−1 and Dq=915 cm−1, B=810 cm−1, C=2780 cm−1, respectively. The presence of various functional groups and the modes of vibrations were confirmed by FTIR studies.

SYNTHESIS AND SPECTROSCOPY OF SOME QUATERNARY OXYFLUORIDE GLASSES DOPPED WITH COPPER

Electron paramagnetic resonance (EPR) and optical absorption spectra of copper ions in xLiF-(50-x)Li2O-20SrO-30Bi2O3 glass system have been studied. MDSC studies showed that the glass transition temperature decreases with LiF content. Optical absorption spectra of the pure glasses reveled that the cut off wave length increased and optical band gap energy decreased with increase in LiF content. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu2+ ions. The Cu2+ ions are in well-defined axial sites but subjected to small distortion leading to the broadening of the spectra. The spin-Hamiltonian parameter values indicate that the ground state of Cu2+ is d x2 y2 and the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The optical absorption spectra exhibited a broad band corresponding to the d-d transition bands of Cu2+ ion. By correlating EPR and optical absorption data, the bond parameters are evaluated from various techniques.

Paramagnetic Ge–Li centres in alpha quartz revisited: The DLi([GeO4/Li]0D) centre

A previously unreported stable paramagnetic defect centre in single-crystal alpha-quartz has been studied by quantitative X-band electron paramagnetic resonance spectroscopy at 15, 100, and 296 K, and is shown to contain a Ge3+ ion, presumably located substitutional for Si4+, with a nearby interstitial Li+ ion. The centre, called DLi herein, grows in slowly (months) after room-temperature x-irradiation and storage. Hyperfine structure arising from 73Ge, 7Li, and 29Si has been observed. The spin-Hamiltonian parameter matrices g, A(7Li), A(73Ge), and P(73Ge) are reported, also for centre CLi. A thermal dynamic process, probably involving Li+ hopping, begins to be appreciable above 100 K. Discussion of DLi, its apparent growth from another paramagnetic centre (not yet fully characterized), and comparison with other similar defects is included.PACS Nos.: 42.70.Ce, 61.72.Hh, 61.72–y, 61.72S–, 61.72uf, 61.80–x, 76.30–v, 76.30.Mi

Electron paramagnetic resonance studies of the E′ centers in alpha-quartz

Room-temperature electron paramagnetic resonance (EPR) studies (at ca. 9.85 GHz) of γ- and x-irradiated alpha-quartz are reported and discussed. The previously described E′2 center has been proved to be associated with hydrogen, and this center’s primary silicon-29 hyperfine coupling matrix has now been accurately determined, as were its hydrogen hyperfine coupling and electronic Zeeman splitting (g) matrices. The paramagnetic center is believed to arise from attack on a diamagnetic oxygen-anion vacancy V(O0) (E center) effectively by an electron and a proton arising from atomic hydrogen produced in the irradiation process. A second very similar center, called E′2(II) herein, was discovered and its parameter matrices too have been obtained by EPR, and it was modelled as described herein. It is proposed that the proton in E′2 resides on an oxygen anion adjacent to the vacancy species. Comparison is made of the spin-Hamiltonian parameter matrices and the choice of best symmetry-related sites expressing them, for the various centers E′1–E′4. PACS Nos.: 76.30.–v,61.72.Hh, 76.30.Mi, 42.70.Ce, 61.80.–x, 61.72.–y

EPR Analysis of Copper Exchanged and Encapsulated Copper (SALEN) Complex in Zeolite - Y

ABSTRACTCopper exchanged and copper-(salen) complex encapsulated in zeolite-Y were prepared. The encapsulaled complex was analysed by TGA, DRS and IR, which confirms the presence of complex in zeolite. Both copper materials were examined by EPR spectra, and the calculated spin-Hamiltonian parameter indicates the copper complex is more covalent in character than NaCu-Y.

The spin-Hamiltonian parameter temperature dependence of the EPR spectra of Gd3+ impurity ions in Y(OH)3 and Eu(OH)3

The 9.23 GHz electron paramagnetic resonance (EPR) spectrum of ~1% Gd3+ impurity ions in Y(OH)3 and Eu(OH)3 monocrystals has been measured from 11 to 296 K. These spectra have been analyzed using a C3h symmetry, phenomenological spin-Hamiltonian. The temperature variation of the spin-Hamiltonian parameters was fitted to empirical root-mean-square (rms) best-fit expressions. It was found that the g values are linear functions of the temperature and that the nearest neighbour (nn) exchange interaction, Jnn = +0.23(5) cm−1 for (Gd3+−Eu3+) ion pairs, can be estimated from the single ion data. This is in satisfactory agreement with Jnn = +0.06(9) cm−1 obtained from ion pair data. The temperature variation of the zero field splitting (ZFS) parameters B20 and B40was found to fit cubic expressions over the temperature measurement interval and the magnitude of B20 increased as the temperature increased, corroborating the earlier conclusion that the host lattice effect in the Ln(OH)3 series cannot be explained using a point charge model for the crystalline electric field.

The magnetic properties of the oxygen–hole aluminum centers in crystalline SiO2. II. [AlO4/H+]+ and [AlO4/Li+]+

The centers [AlO4/M+]+, formed in α-quartz by X-irradiation at 77 K, contain an aluminum ion substituted for a silicon ion, with an electron removed from a neighboring oxygen by the ionizing radiation. In addition, there is an interstitial ion M+ which acted as a charge compensator before the irradiation. Centers [AlO4/H+]+ and [AlO4/Li+]+ have been re-examined by EPR (at ca. 35 K), including measurement of small hyperfine splittings due to the compensator ions. The spin-Hamiltonian parameter matrices (i.e., [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) show that the hole-trapping oxygen in these species is linked via a "short" bond to aluminum (there are two different Si–O bond lengths in quartz). The probable positions of the compensating ions (Li+, H+) in a channel parallel to the crystallographic c-axis are reported.