SPECTROSCOPIC STUDIES OF EXCHANGE INTERACTIONS IN POLYNUCLEAR TRANSITION METAL COMPLEXES II. [(NH3)5Cr(OH)Cr(NH3)5] Cl5,3H20.

1973 ◽  
Vol 26 (3) ◽  
pp. 513 ◽  
Author(s):  
J Ferguson ◽  
H.U Gudel ◽  
M Puza
Keyword(s):  
Room Temperature ◽  
Energy Levels ◽  
Exchange Interactions ◽  
Structural Disorder ◽  
Spectroscopic Properties ◽  
Spectroscopic Studies ◽  
Stable Form ◽  
Strongly Coupled ◽  
Crystal Forms ◽  
Chloride Monohydrate

Single crystals of phydroxo-bis[pentaamminechromium(III)] chloride monohydrate have been prepared. The spectroscopic properties of these crystals have been measured and two crystal forms have been characterized. The first form is obtained from solutions at 2�C and it changes to the second, stable form, at room temperature. The latter is tetragonal, space group D44-P41212 with a = 16.28 %L, c = 14.84 A, and Z = 8. The spectroscopic properties require two inequivalent sets of dimer units in the unit cell and this result is consistent with the X-ray data. The spectroscopic properties of the first form require four inequivalent sets of dimers and the ground state energy levels of each of these are described by the isotropic Hamiltonian H = JSa . Sb - j(Sa. Sb)2 with the following values: set 1, J = 30.4+/- 0.2, j = 0.32+/-0. 10; set 2, J = 30.4 +/-0.2, j = 0.221 0.10; set 3, J = 31.4 +/-0.2, j = 0-18+/- 0.10; set 4, J = 31-4+/- 0.4, j = 0.0+/- 0.20. High-resolution luminescence excitation spectroscopy shows that sets 1 and 2 are not strongly coupled to sets 3 and 4. The small differences between sets 1 and 2 and between sets 3 and 4 suggest that these differences arise from structural disorder within the two inequivalent sets of the room temperature stable form. Previous differences in the interpretation of the earlier magnetic and

SPECTROSCOPIC STUDIES OF EXCHANGE INTERACTIONS IN POLYNUCLEAR TRANSITION METAL COMPLEXES I. [(NH3)5Cr(OH)Cr(NH3)5] Cl5,3H20.

1973 ◽  
Vol 26 (3) ◽  
pp. 505 ◽  
Author(s):  
J Ferguson ◽  
HU Gudel
Keyword(s):  
Absorption Spectrum ◽  
Single Crystals ◽  
Transition Metal Complexes ◽  
Level Scheme ◽  
Exchange Interactions ◽  
Spectroscopic Properties ◽  
Spectroscopic Studies ◽  
Luminescence Spectra ◽  
Weakly Coupled ◽  
Chloride Trihydrate

Large single crystals of ,u-hydroxo-bis[pentaamminechromium(III) chloride trihydrate have been prepared and their spectroscopic properties determined. The analysis of polarized single-crystal luminescence spectra provides an accurate ground electronic level scheme for the weakly coupled chromium ions in the dimeric cluster. The splitting is described by the isotropic Hamiltonian X = JS,.Sb-j(S,.Sb)2 with J = 31.9 cm-1 and j = 0.23 cm-1. The temperature dependence of the polarized absorption spectrum is consistent with this level scheme. The positions of the components of the singly excited (4A2-2E) state have been determined.

Spectroscopic Properties of Cubic SiC on Si

2002 ◽  
Vol 742 ◽  
Author(s):  
Z. C. Feng ◽  
D. N. Talwar ◽  
I. Ferguson
Keyword(s):  
Room Temperature ◽  
Vapour Deposition ◽  
Function Theory ◽  
Chemical Vapour ◽  
Spectroscopic Properties ◽  
Spectroscopic Studies ◽  
Room Temperature Photoluminescence ◽  
Raman Modes ◽  
Indirect Band Gap ◽  
Uv Excitation

ABSTRACTSpectroscopic studies are reported for cubic SiC grown on Si by chemical vapour deposition (CVD) manufacture technique. The UV excitation room temperature photoluminescence (PL)-Raman spectra exhibited 2.3 eV luminescence line due to RT recombination over the SiC indirect band gap. In addition to the optical phonons from cubic SiC we observed new Raman modes near 620 and 833 cm-1. A comprehensive analysis of the dynamical properties of defects using Green's function theory has suggested isolated impurity vibrations to be the possible origin for the additional phonons observed by Raman spectroscopy.

scholarly journals Isospin-1/2 Dπ scattering and the lightest $$ {D}_0^{\ast } $$ resonance from lattice QCD

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Luke Gayer ◽  
Nicolas Lang ◽  
Sinéad M. Ryan ◽  
David Tims ◽  
Christopher E. Thomas ◽  
...  
Keyword(s):  
Scattering Amplitudes ◽  
Lattice Qcd ◽  
Quark Mass ◽  
Light Quark ◽  
Energy Levels ◽  
Experimental Result ◽  
Infinite Volume ◽  
Resonance Pole ◽  
Strongly Coupled ◽  
Light Quark Mass

Abstract Isospin-1/2 Dπ scattering amplitudes are computed using lattice QCD, working in a single volume of approximately (3.6 fm)3 and with a light quark mass corresponding to mπ ≈ 239 MeV. The spectrum of the elastic Dπ energy region is computed yielding 20 energy levels. Using the Lüscher finite-volume quantisation condition, these energies are translated into constraints on the infinite-volume scattering amplitudes and hence enable us to map out the energy dependence of elastic Dπ scattering. By analytically continuing a range of scattering amplitudes, a $$ {D}_0^{\ast } $$ D 0 ∗ resonance pole is consistently found strongly coupled to the S-wave Dπ channel, with a mass m ≈ 2200 MeV and a width Γ ≈ 400 MeV. Combined with earlier work investigating the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ , and $$ {D}_0^{\ast } $$ D 0 ∗ with heavier light quarks, similar couplings between each of these scalar states and their relevant meson-meson scattering channels are determined. The mass of the $$ {D}_0^{\ast } $$ D 0 ∗ is consistently found well below that of the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ , in contrast to the currently reported experimental result.

scholarly journals Temperature-Dependent Stimulated Emission Cross-Section in Nd3+:YLF Crystal

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 431
Author(s):  
Giorgio Turri ◽  
Scott Webster ◽  
Michael Bass ◽  
Alessandra Toncelli
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Room Temperature ◽  
Radiative Decay ◽  
Emission Cross Section ◽  
Spectroscopic Properties ◽  
Stimulated Emission ◽  
Different Temperatures ◽  
Stimulated Emission Cross Section ◽  
Semi Empirical

Spectroscopic properties of neodymium-doped yttrium lithium fluoride were measured at different temperatures from 35 K to 350 K in specimens with 1 at% Nd3+ concentration. The absorption spectrum was measured at room temperature from 400 to 900 nm. The decay dynamics of the 4F3/2 multiplet was investigated by measuring the fluorescence lifetime as a function of the sample temperature, and the radiative decay time was derived by extrapolation to 0 K. The stimulated-emission cross-sections of the transitions from the 4F3/2 to the 4I9/2, 4I11/2, and 4I13/2 levels were obtained from the fluorescence spectrum measured at different temperatures, using the Aull–Jenssen technique. The results show consistency with most results previously published at room temperature, extending them over a broader range of temperatures. A semi-empirical formula for the magnitude of the stimulated-emission cross-section as a function of temperature in the 250 K to 350 K temperature range, is presented for the most intense transitions to the 4I11/2 and 4I13/2 levels.

scholarly journals Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christian Wiebeler ◽  
Joachim Vollbrecht ◽  
Adam Neuba ◽  
Heinz-Siegfried Kitzerow ◽  
Stefan Schumacher
Keyword(s):  
Absorption Spectra ◽  
Density Functional ◽  
Energy Levels ◽  
Spectroscopic Properties ◽  
Absorption Bands ◽  
Functional Theory ◽  
Vertical Excitation ◽  
Hartree Fock ◽  
Tauc Plot ◽  
Electrochemical Approach

AbstractA detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree–Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands.

scholarly journals Probing resonating valence bond states in artificial quantum magnets

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kai Yang ◽  
Soo-Hyon Phark ◽  
Yujeong Bae ◽  
Taner Esat ◽  
Philip Willke ◽  
...  
Keyword(s):  
Quantum Information Processing ◽  
Energy Levels ◽  
Finite Size ◽  
Valence Bond ◽  
Exchange Interactions ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Many Body ◽  
Quantum Magnets ◽  
Resonating Valence Bond

AbstractDesigning and characterizing the many-body behaviors of quantum materials represents a prominent challenge for understanding strongly correlated physics and quantum information processing. We constructed artificial quantum magnets on a surface by using spin-1/2 atoms in a scanning tunneling microscope (STM). These coupled spins feature strong quantum fluctuations due to antiferromagnetic exchange interactions between neighboring atoms. To characterize the resulting collective magnetic states and their energy levels, we performed electron spin resonance on individual atoms within each quantum magnet. This gives atomic-scale access to properties of the exotic quantum many-body states, such as a finite-size realization of a resonating valence bond state. The tunable atomic-scale magnetic field from the STM tip allows us to further characterize and engineer the quantum states. These results open a new avenue to designing and exploring quantum magnets at the atomic scale for applications in spintronics and quantum simulations.

Crystal Structures of and Polarized Absorption-Spectroscopy in Racemic and Resolved [Ru(bpy)3] (ClO4)2 and [Zn(bpy)3] (ClO4)2Bpy=2,2'-Bipyridine

1995 ◽  
Vol 48 (5) ◽  
pp. 929 ◽  
Author(s):  
E Krausz ◽  
H Riesen ◽  
AD Rae
Keyword(s):  
Room Temperature ◽  
Energy Difference ◽  
Temperature Structure ◽  
Asymmetric Unit ◽  
Threefold Axis ◽  
Crystal Forms ◽  
The Third ◽  
Racemic Form ◽  
Ligand Charge Transfer ◽  
Dominant Influence

[Zn( bpy )3] (ClO4)2 and [ Ru ( bpy )3] (ClO4)2 are isomorphous in both their racemic and resolved crystal forms. The resolved materials are monohydrates and have a C 2, Z = 8, structure with two independent formula units on general sites in the asymmetric unit. The cations have the same chirality. The inherent threefold axis of each cation lies approximately parallel to the c axis. The unrelated racemic form has a C2/c, Z = 4, structure which is a commensurate modulation of a P3c1, Z = 2, parent structure, typified by the room-temperature structure of [ Ru ( bpy )3] (PF6)2. A primary, secondary and tertiary axis of P3c1 become the c, b and a axes respectively of C2/c, retaining a third of the symmetry elements of P3c1. The crystals grow as multiply contacted twins. This structure bas just one spectroscopic site with the cation lying on a twofold axis that passes through the metal and one of the bidendate ligands and relates the other two ligands to each other. This feature is particularly useful in the study of the optical spectroscopy of the metal-to- ligand charge transfer excitations of [ Ru ( bpy )3]2+ and related systems. A comparison of structural and spectral data indicates that the positions of the anions have a dominant influence on the relative energies of the metal-to- ligand excitations. An energy difference between excitations involving the two (lower-energy) equivalent ligands and the third ligand of the order of 800 cm-1 is indicated in both singlet and triplet regions for the racemic perchlorate. The absorption spectra of [ Ru ( bpy )3]2+and [Os( bpy )3]2+ in a number of crystalline hosts are compared and discussed.

scholarly journals Insertion of Phosphenium Ions into a Bicyclo[1.1.0]Tetraphosphabutane Iron Complex

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3920
Author(s):  
Martin Weber ◽  
Gábor Balázs ◽  
Alexander V. Virovets ◽  
Eugenia Peresypkina ◽  
Manfred Scheer
Keyword(s):  
Diffraction Analysis ◽  
Room Temperature ◽  
31P Nmr ◽  
Spectroscopic Studies ◽  
Iron Complex ◽  
The Novel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phosphenium Ions

By reacting [{Cp‴Fe(CO)2}2(µ,η1:1-P4)] (1) with in situ generated phosphenium ions [Ph2P][A] ([A]− = [OTf]− = [O3SCF3]−, [PF6]−), a mixture of two main products of the composition [{Cp‴Fe(CO)2}2(µ,η1:1-P5(C6H5)2)][PF6] (2a and 3a) could be identified by extensive 31P NMR spectroscopic studies at 193 K. Compound 3a was also characterized by X-ray diffraction analysis, showing the rarely observed bicyclo[2.1.0]pentaphosphapentane unit. At room temperature, the novel compound [{Cp‴Fe}(µ,η4:1-P5Ph2){Cp‴(CO)2Fe}][PF6] (4) is formed by decarbonylation. Reacting 1 with in situ generated diphenyl arsenium ions gives short-lived intermediates at 193 K which disproportionate at room temperature into tetraphenyldiarsine and [{Cp‴Fe(CO)2}4(µ4,η1:1:1:1-P8)][OTf]2 (5) containing a tetracyclo[3.3.0.02,7.03,6]octaphosphaoctane ligand.

Optical Spectroscopic Studies of a Soluble Fluorene-Based Conjugated Polymer: A Hydrostatic Pressure and Temperature Study

2001 ◽  
Vol 708 ◽  
Author(s):  
S. Guha ◽  
J.D. Rice ◽  
C. M. Martin ◽  
W. Graupner ◽  
M. Chandrasekhar ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Conjugated Polymer ◽  
Spectroscopic Properties ◽  
Spectroscopic Studies ◽  
Phonon Interaction ◽  
Optical Studies ◽  
Strong Electron ◽  
Conjugated Molecules ◽  
Electron Phonon Interaction ◽  
Backbone Conformation

ABSTRACTSpectroscopic properties of conjugated molecules/polymers have varying degrees of sensitivity to backbone conformation. Optical studies are presented as a function of temperature and hydrostatic pressure, using photoluminescence and Raman scattering from two polymers with distinct differences in their backbone conformation, namely, polyfluorene (PF) and ladder type poly(para-phenylene)(m-LPPP). In contrast to the photoluminescence (PL) vibronics in mLPPP, the 0-0 PL vibronic peak in PF shows a red-shift with increasing temperatures. Pressure studies reveal that the PL spectrum of PF red-shifts and broadens with increasing pressures. The phonon lines in PF show an antiresonance effect at higher pressures indicating a strong electron-phonon interaction.

scholarly journals Spectroscopic Studies of Er3+-Yb3+ Codoped Multicomposition Tellurite Oxide Glass

2014 ◽  
Vol 895 ◽  
pp. 323-333 ◽  
Author(s):  
Sharudin Omar Baki ◽  
L.S. Tan ◽  
C.S. Kan ◽  
Halimah Mohamed Kamari ◽  
A.S.M. Noor ◽  
...  
Keyword(s):  
Room Temperature ◽  
Near Infrared ◽  
Transition Probabilities ◽  
Branching Ratios ◽  
Spectroscopic Studies ◽  
Oxide Glass ◽  
Near Infrared Spectra ◽  
Intensity Parameters ◽  
Measured Absorption

Multicomposition of Er3+-Yb3+codoped tellurite oxide, TeO2-ZnO-PbO-TiO2-Na2O glass has been investigated. Detailed spectroscopic study of the Judd-Ofelt analysis has been performed from the measured absorption spectrum in order to obtain the intensity parameters Ωt(t=2, 4, 6). The calculated Ωtvalues were then utilized in the determination of transition probabilities, radiative lifetimes and branching ratios of the Er3+transitions between theJ(upper)-J(lower) manifolds. Both visible upconversion and near-infrared spectra were characterized under the 980 nm laser diode excitation at room temperature.

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