Showing papers on "Spin states published in 1983"

ESR of Mn2 and Mn5 molecules in rare‐gas matricesa)

Abstract: Mn2 and Mn5 have been isolated in argon, krypton, and xenon matrices and their X‐band ESR spectra observed at 4 and up to 70 K, depending upon the matrix. As predicted by Nesbet, the lowest state of Mn2 is 1Σ, and the two atoms are exchange coupled (antiferromagnetically). The temperature behavior of the ESR bands in the higher spin states (S=1,2,3) was approximately in accord with a Lande interval rule, and a value of J=−9±3 cm−1 was obtained from the S=2 intensity variations. Each fine structure line appears with a superimposed 11‐line hyperfine pattern with splitting one‐half that of isolated 55Mn atoms (30 G). The anisotropic exchange interactions fit the Judd–Owen relationship with De=−0.043(2) and Dc=−0.001(4) cm−1. Assuming De arises solely from magnetic dipole interaction, the interatomic distance in Mn2 is calculated to be 3.4 A. Mn5 appears in more concentrated matrices as a highly oriented axial molecule with its axis perpendicular to the flat sapphire substrate surface. The observed fine struc...

Electron transfer between magnetic ions in mixed valence binuclear systems

Abstract: This paper describes how the Hubbard model in the atomic limit implemented by taking into account molecular vibrations can give a description of mixed valence binuclear systems with both metallic ions simultaneously magnetic. A FeIII (high spin) FeII (high spin) binuclear complex would constitute an example. In such systems electron transfer and electron exchange are expected. If the compound belongs to class II (Robin and Day classification) we find that the activation energy of the thermal electron transfer and the intensity of the intervalence band are spin dependent but that the energies of spin states are given by the Heisenberg Hamiltonian with a new expression for the exchange parameter. For class III binuclear complexes a quite different behavior is found. The energy of the intervalence band is spin dependent but energies of spin states are no longer given by the Heisenberg Hamiltonian.

Single Crystal Magnetic Study on Ferromagnetic Manganese (II) Phthalocyanine.

Abstract: : A magnetic study has been carried out in the temperature range 1.2-25 K and magnetic field range 0 to 50 kOe on single crystals of manganese (II) phthalocyanine. At higher temperatures the magnetic properties of manganese (II) phthalocyanine exhibit chain-like characteristics which may be understood in terms of ferromagnetic Heisenberg intrachain exchange of S = 3/2 ions with a weak antiferromagnetic interchain interaction. In the ordered state, Tc, = 8.3 K, MnPc is a canted ferromagnet with easy axes of magnetization being along X1 and X3 directions. A zero-field splitting of the single ion 4A2 state of the manganese (II) ion gives rise to canted ferromagnetism which does not show complete saturation at the high field range of these experiments (50 kOe). The spin structure of manganese (II) phthalocyanine at low temperature is discussed. (Author)

Atomic masses above 146 Gd derived from a shell model analysis of high spin states

Abstract: From a shell model analysis of high-spin states in neutron deficient nuclei above146Gd we have derived the ground state masses of theN=82 and 83 isotones of Eu, Tb, Dy, Ho, and Er. The results can be used to calculate the energies of aligned multiparticle yrast configurations. They also link ten α-decay chains to the nuclei with known masses, providing many new absolute mass values which are compared with predictions. An examination of the two-proton separation energies atN=82 shows an 0.5 MeV break in the nuclear mass surface atZ=64.

A CHELATE RING SIZE EFFECT ON SPIN STATES OF IRON(III) COMPLEXES WITH HEXADENTATE LIGANDS DERIVED FROM SALICYLALDEHYDE AND 4,8-DIAZAUNDECANE-1,11-DIAMINE(3,3,3-tet) OR 4,7-DIAZADECANE-1,10-DIAMINE(3,2,3-tet), AND THEIR X-RAY STRUCTURES

Abstract: High- and low-spin Fe(III) complexes with the titled ligands, [Fe(Sal23,3,3-tet)](NO3) (S=5/2) (1) and [Fe(Sal23,2,3-tet)](NO3) (S=1/2) (2), have been synthesized. X-ray analyses for 1 and 2 show that, in each complex, the metal environment is pseudo octahedral with the two O atoms being trans. Difference of one CH2 group in the methylene chain of the ligand causes a copmlete change in the spin state without changing coordination gemetries. In methanol, 2 is essentially low spin with μeff=1.95 BM(263.5 K), whereas 1 exhibits the behavior for the spin equilibrium [μeff=3.00(244.5 K)–4.04(305.5 K) BM]. The equilibrium constant of 1, K = [low-spin]/[high-spin]=2.6±0.9 at 25 °C and ΔH = −11.8±2.5 kJ mol−1 were obtained from detailed analyses of the temerature dependent electronic spectra.

Redox reactions of variable-spin six-coordinate bis(N-R-2,6-pyridinedicarboxaldimine)cobalt(II) complexes

Abstract: Etude de l'effet de l'etat de spin sur les proprietes de transfert d'electrons de la famille des complexes hexacoordines, a spin variable, de bis(N-R-pyridinedicarboxaldimine-2,6) cobalt(II), ou R=C(CH 3 ) 3 , CH(CH 3 ) 2 , p-PhCH 3 et CH 2 Ph, en milieu non aqueux. Etude des 2 reactions d'electrode de Co 3+ /Co 2+ et de Co 2+ /Co +

Coordination chemistry of microbial iron transport compounds. 25. Proton-dependent cobalt(III) spin states. Structure of the sodium salt of trans-tris(benzohydroximato)cobaltate(III)

Abstract: Complexes of cobalt(II1) with hydroxamic acids [RC(O)N(OH)R'] are described. Coordination occurs through the two oxygen atoms after the loss of the NOH proton. For tris(hydroxamate) complexes with R' = alkyl the complexes are low spin; when R' = H or when R contains an electron-withdrawing group, the complexes are paramagnetic. However, the tris(hydroximato)cobaltate(III) trianion complexes, which result from further deprotonation of the hydroxamate complexes when R' = H, are low spin. Thus there is a reversible, proton-dependent transition between low- and high-spin states in the hydroximate and hydroxamate complexes. An unusual feature of the Co(II1) complexes is that, while the low-spin hydroximato [CoL3I3- complex is thermally stable, the high-spin hydroxamato [CO(HL),]~ complex ultimately undergoes an internal redox reaction resulting in oxidation of the ligand by the metal ion. The structure of the (nitrogen deprotonated) trans isomer of tris(benzohydroximato)cobaltate(III), as the salt Na3 [CO(C~H,NO~)~].~H~O-C~H~OH, has been determined by single-crystal X-ray diffraction techniques with data obtained by counter methods. The material crystallizes as dark green prisms in the monoclinic space group P2Jn with a = 10.360 (1) A, b = 11.1 18 (2) A, c = 28.403 (5) A, p = 93.64 (1)' and is isostructural with the previously reported Cr(II1) complex. The Co(II1) complex possesses a trans geometry in which the Oc and ON atoms of one chelate ring are trans to an Oc and an ON atom of one of the other two chelate rings. The coordination geometry about Co(II1) approximates that of a trigonally distorted octahedron. As in the structure of the Cr(II1) complex, the lengthening of the C-0 bonds and the shortening of the C-N bonds indicate that much of the negative charge on the deprotonated nitrogen atoms is delocalized over the N-C=O portions of the ligands. The calculated (1.47) and measured (1.44 g ~m-~) densities are consistent with four formula units of the salt per unit cell. Full-matrix least-squares refinement of the structure with use of the 3906 reflections with F: > 3u(F:) have converged with R and R, indices of 0.035 and 0.048, respectively.

Nuclear Magnetic Resonance of 89 Y in Intermetallic Compounds Y(Fe 1-x Mn x ) 2

Abstract: The NMR spectra of 89 Y have been observed at 4.2 K to investigate the magnetic properties of Y(Fe 1- x Mn x ) 2 . There are two kinds of Mn moments in low Mn-concentrations; one is antiparallel to the Fe moment and estimated to be 0.5 µ B per Mn (low spin state), and the other is parallel to the Fe moment and has 2.7 µ B per Mn (high spin state).

High spin states in 91 Tc

Abstract: A shell model calculation for the states of91Tc has been carried out using the (1g9/2, 2p1/2) model space with residual interactions determined from previous studies and assuming thatZ=38N=50 is a closed shell. The results, both for the spectrum and the gamma decay modes, support the experimental angular momentum assignments made for the high spin states. The predicted binding energy of the 9/2+ ground state relative to88Sr is within 75 keV of the experimental value and the calculated excitation energy of the 1/2− state is 183 keV. There is only one instance where theory and experiment disagree: the highest energy excited state, the 41/2− at 7.715 MeV, is predicted to undergo quadrupole decay to the 37/2− and this decay mode is not seen.

Excited states in 145 Gd from the ( 3 He, 2 n ) reaction

Abstract: Medium and high spin states in145Gd up to 3.5 MeV excitation energy have been studied by in-beam gamma ray and conversion electron spectroscopy bombarding enriched144Sm target with a3He beam. For a part of the identified levels a configuration is proposed in terms of weak coupling of one neutron hole with the146Gd core or of one neutron particle with the144Gd core.

Yrast transition strengths in 85 Rb and 85 Sr

Abstract: High spin states in85Rb and85Sr were populated in the reactions76Ge(12C,p2n) and76Ge(12C,3n), respectively. The lifetimes of twelve states were measured via the recoil distance Doppler shift technique. The positive parity bands in both nuclei associated with theg 9/2 orbit exhibit decrasingE2 strengths for increasing spin value marking the onset of multiparticle excitation.

Low-spin states in even po and rn isotopes and the interplay between collective and quasiparticle configurations

Abstract: Low-spin states in even Po and Rn isotopes are studied within the framework of the interacting-boson-approximation + two-quasiparticle model. The irregular behavior of the 4/sup +/ levels is shown to result from an interplay between collective, quasiproton, and quasineutron states. Some predictions are made for the corresponding Ra isotopes.

The discontinuous volume change in transition-metal compounds due to the pressure-induced spin-state transition

Abstract: Several transition-metal compounds change their volume abruptly under high pressure through their electronic spin-state transition. The pressure-induced spin-state transitions in transition-metal compounds are studied on the basis of the ligand-field theory by using the model in which the coupling of transition-metal ions with crystal distortions is taken into account. The various types of transitions occur due to the crystal distortion induced by pressure, that is, the continuous and discontinuous high-spin (HS) to low-spin (LS) transitions with increasing pressure in the weak-crystal-field compounds, the continuous and discontinuous LS to HS transitions and the multiple LS to HS to LS to HS transition in the strong-crystal-field compounds. The pressure against volume curve shows various features of changes due to the crystal distortion associated with the spin-state transitions. The observed pressure against volume curve of haematite Fe2O3 is well explained by the discontinuous HS to LS transition of Fe3+ ions.

Measurement of the difference in pp total cross sections for pure parallel and antiparallel transverse-spin states (. delta. sigmasubT) at Tsubp = 487, 639, and 791 MeV

Abstract: The difference between total cross sections in pure transverse-initial-spin states for the p-p interaction has been measured at Tsubp = 487, 639, and 791 MeV, using a frozen-spin target. A comparison with previous data and available phase-shift analyses is made.