Natural radiative lifetimes in the2 S 1/2 and2 D 3/2, 5/2 sequences of neutral copper

Natural radiative lifetimes have been measured of the 3d ¹⁰ ns ² S _1/2 (n=6?10) and of the 3d ¹⁰ nd ² D _{3/2, 5/2} (n=5?9) sequences by using two step excitation of copper atoms in an atomic beam. The states investigated were populated by the light from two pulsed dye lasers pumped by the same Nd:YAG laser. The lifetimes of the² D sequence increase regularly with increasing principal quantum number. This is not the case for the² S series, because of configuration interaction in the² P series. In addition the lifetime of the 3d ¹⁰5p ² P _3/2 state has been measured together with its branching ratio.     

Hyperfine structure in the configurations4f 4 6s 2 and4f 4 5d 6s of Nd I

The high resolution laser-atomic-beam technique was used to investigate the hyperfine structure in Nd I 4f ⁴6s ^{2 5} I,⁵ F,⁵ S and 4f ⁴5d6s ⁷ L,⁷ K,⁷ I,⁷ H. The metastable states were populated by an arc discharge burning in the atomic beam. The measured hyperfine constantsA andB of the levels of 4f ⁴6s ² and 4f ⁴5d6s allow a parametric analysis to be performed using the effective tensor operator formalism. The experimental radial integrals of the 4f and 5d electrons fit with those of the other lanthanides. The 4f radial integrals are in agreement with values of optimized Hartree-Fock-Slater calculations. The spectroscopic quadrupole moments of¹⁴³Nd and¹⁴⁵Nd are deduced from the 4f parameters:Q _I =?0.610(21) b and ?0.314(12) b, respectively. TheQ _I resulting from the 5d parameter are in satisfactory agreement with these values. The hyperfine anomaly due to thes electron in 4f ⁴5d 6s amounts to about 1%.     

Hyperfinestructure-investigations in the mangan I configurations 3d 5 4s 4p and 4s 5s

Nine transitions (ranging from 475 till 733 nm) between the excited configuration 3d ⁵ 4s 5s and 3d ⁵ 4s 4p of⁵⁵Mn were investigated with computer supported interference spectroscopy. Thus the hyperfine structure (hfs) of the four 4s 5s and the twelve 4s 4p levels is now completely known from experiment. The hfs results are discussed with the effective operator technique and for 4s 4p the accuracy of the one-electron parametersa ^ik could be improved:a _3d ¹⁰ =?6.28(24),a _4s ¹⁰ =154.0(1.4),a _4p ⁰¹ =9.3(8),a _4p ¹² =7.7(2.5) in mK. For the configuration 4s 5s — for which fine structure calculations are not yet available — the experimental hfs data prove a practically pureS-character. Besides the one-electron splitting parameters deduced:a _3d ¹⁰ =?6.5(5),a _4s ¹⁰ =182(3),a _5s ¹⁰ =24(3) in mK, permit to determine the degree of mixing between the twoe ⁶ S _5/2 andf ⁶ S _5/2 levels which amounts to about 3%.     

Alignment of atoms following photoionisation: Cd+(4d −1 2 D 5/2,2 D 3/2) and Zn+(3d −1 2 D 3/2)

The linear polarisation of fluorescence radiation following the photoionisation in the 4d _5/2 and 4d _3/2 subshells of Cd and in the 3d _3/2 subshell of Zn has been measured in the energy range of primary photons from threshold up to about 40 eV. The experimental values of the linear polarisation found for the fluorescence radiation of Cd⁺(4d ^?1) ions are in essential agreement with theoretical results obtained by an RRPA calculation (Johnson et al.). For the case of Zn⁺(3d ^?1) on the other hand, no theoretical data are presently available. Using the experimental values of linear polarisation of fluorescence radiation the values of the alignment tensorA ₂₀ have been evaluated for the ions Cd⁺(4d ^{?1 2} D _5/2,² D _3/2) and Zn⁺(3d ^{?1 2} D _3/2).     

Observation of the electric-field-inducedE1 transition between 5s4d 1 D 2 and 5s 2 1 S 0 levels in Sr I

The angular distribution of the electric-field-inducedE1 radiation is asymmetric with respect to the external electric field direction. Measurement of this asymmetry for the 5s4d ¹ D ₂ → 5s ^{2 1} S ₀ transition in strontium permits the experimental determination of the 5s5p ¹ P ₁ → 5s4d¹ D ₂ decay rate. The result is:A(¹ P ₁ →¹ D ₂)=(4.37±0.93±0.66) × 10³ s ^?1.     

Lifetime measurements of the 3d 94s(1 D) 4p configuration of Cu I

The radiative lifetimes of the levels in the 3d ⁹4s(¹ D)4p configuration of Cu I are measured. The levels are excited from the metastable 3d ⁹4s ^{2 2} D _3/2,5/2 levels. The metastable Cu atoms are generated in a pulsed hollow cathode discharge. The levels investigated are populated with a 35-ps laser pulse at wavelengths around 220 nm. The laser induced fluorescence signal is detected. The lifetime of the 3d ⁹4s(³ D)4p ⁴ D _1/2 level is also determined by direct excitation from the ground state. A comparison with calculated literature values is given.     

Ta4P4S29: A new tunnel structure with inserted polymeric sulfur

Ta₄P₄S₂₉ was prepared from the elements heated together in stoichiometric proportions in an evacuated Pyrex tube for 10 days at 500°C. The crystal symmetry is tetragonal, space group P4₃2₁2, with the cell parameters: a = b = 15.5711(7) Å, c = 13.6516(8) Å, V = 3309.9(5) ų, and Z = 4. The structure calculations were conducted from 2335 reflections and 146 variables, leading to R = 0.033. The structure basic framework, corresponding to the chemical composition [TaPS₆], is made of biprismatic bicapped [Ta₂S₁₂] units (average d_TaS = 2.539 Å), including sulfur pairs (average d_SS = 2.039 Å), bonded to each other through [PS₄] tetrahedral groups (average d_PS = 2.044 Å) sharing sulfurs. This framework leaves large tunnels running along the c axis of the cell and in which (S₁₀)_∞ sulfur chains are found to be inserted (average d_SS = 2.052 Å and SSS = 105.75°). Diamagnetic and semiconducting Ta₄P₄S₂₉ can be formulated: Ta^V₄P^V₄(S^?II)₁₆(S^?II₂)₄(S⁰₅).     

Synthesis and structure determination of a new layered compound: V2P4S13

V₂P₄S₁₃ was prepared from the elements taken in stoichiometric proportions and heated in an evacuated Pyrex tube for 10 days at 450°C. The crystal symmetry is triclinic, space group P1¯ with the parameters: a = 9.112(1) Å, b = 9.680(1) Å, c = 11.620(1) Å, α = 72.15(1)°, β = 110.82(1)°, γ = 110.13(1)°, V = 879.5(1) ų, and Z = 2. The structure was solved from 3052 independent reflections and 173 parameters, the least-squares refinement yielding R = 0.033. The building units of the structure are made up of two distorted (VS₆) octahedra and four distorted (PS₄) tetrahedra sharing edges to form (V₂P₄S₁₆) groups. These share sulfur atoms through their four (PS₄) tetrahedra with the same neighbor groups. Infinite (V₂P₄S₁₃) planes parallel to (101) are thus obtained, with no bonds other than van der Waals' ones between them. Within the slabs, the layered phase presents the following average distances: d_V-S = 2.471(1) Å, d_P-S = 2.050(1) Å, d_V-V = 3.715(2) Å. From the various oxydation states of the atoms, the developed formula can be written V^III₂P^V₄S^?II₁₃. The phase is semiconducting and magnetic susceptibility measurements show a Curie behavior with the occurrence of high spin d² vanadium. Antiferromagnetic ordering is observed below 10 K.     

Final-state effects in the 3d and 4d X-Ray photoelectron spectra of CeO2

The complex 3d and 4d X-ray photoelectron spectra of CeO₂ arc re-interpreted with the aid of multiple scattering Xα and intermediate coupling calculations. Features in the 3d spectrum are identified with Ce 3d⁹4f⁰, 3d⁹4f¹VB^?1, and 3d⁹5p⁵np final-state configurations. Multiplet coupling in the 3d⁹4f¹ system is found to be significant.     

Die Reaktionen von Trithiazylchlorid mit Zirkoniumtetrachlorid Die Kristallstruktur von (S4N4CI)2[Zr2CI10]

Reactions of Zirconium Tetrachloride with Trithiazylchloride. Crystal Structure of (S₄N₄)[Zr₂Cl₁₀] Zirconium tetrachloride reacts with (NSCI)₃ yielding (S₃N₃CI₂)₂[Zr₂CI₁₀], S₄N₄[Zr₂CI₁₀], or (S₄N₄CI)₂[Zr₂CI₁₀], depending of the reaction conditions. These compounds were characterized by their i.r. spectra. They have an ionic structure containing the known ions S₃N₃CI₂⊕, S₄N₄^2⊕, S₄N₄CI^⊕, and the thus far unknown [Zr₂CI₁₀]^2? ion. According to the X-ray structure determination (2827 independent observed reflexions, R = 0.027), (S₄N₄CI)₂[Zr₂CI₁₀] crystallizes in the space group P&1macr; with the lattice constants a = 688, b = 1132, c = 1827 pm, α = 103.2°, β = 98.7° and γ = 91.9⁰ and with Z = 2 formula units per unit cell. The structure is built up from S₄N₄CI^⊕ ions, which are nearly identical as in S₄N₄CI[FeCI₄] and from [Zr₂CI₁₀]^2? ions in which two chloro bridges join two edge-sharing octahedra.     

Precision measurement of the energy of the 4d 9 5s 2 2 D 5/2 metastable level in Ag I

The energy of the 4d ⁹ 5s ^{2 2} D _5/2 metastable level in Ag I, which is the upper level of the very narrow 5s ² S _1/2 – 4d ⁹ 5s ^{2 2} D _5/2 two-photon transition at 661.2 nm, has been determined from precision measurements of the wavelengths of the 206.1 nm (5s ² S _1/2 – 6p ² P ₃ ^2/0 ) and 547.5 nm (4d ⁹ 5s ^{2 2} D _5/2 – 6p ² P ₃ ^2/0 ) lines emitted from a hollow-cathode discharge. The measured energy of the 4d ⁹ 5s ^{2 2} D _5/2 level, 30 242.286(7) cm^–1, is combined with the known hyperfine splittings and the estimated¹⁰⁷Ag-¹⁰⁹Ag isotope shift to obtain accurate absolute frequencies for the hyperfine components of the 661.2 nm transition. These results should help in the detection of the narrow 661.2 nm two-photon transition, which has been proposed as a new optical frequency standard.     

Synthesis,crystal growth and structure,magnetic and electrical properties of Ba4Ru2FeO10 and Ba4Ru2CoO10

Crystals of Ba₄Ru₂FeO₁₀ and Ba₄Ru₂CoO₁₀ (Cmca, Z = 4, Ba₄Ru₂FeO₁₀: a = 5.7899(1) Å, b = 13.2898(3) Å, c = 13.0098(4) Å, V = 1001.06 Å³; Ba₄Ru₂CoO₁₀: a = 5.7691(2) Å, b = 13.2061(3) Å, c = 12.9755(4) Å, V = 988.57 Å³) were obtained from binary oxides and BaCoO₃ at 1300 °C. Both compounds crystallize isostructural to Ba₄Ru₃O₁₀ with different preference of the 3d metal at the two crystallographic sites of Ru in the parent compound. Ba₄Ru₂FeO₁₀ exhibits a spin-glass like transition at 25 K, while Ba₄Ru₂CoO₁₀ does not show any magnetic order down to 2 K. According to electrical resistivity measurements performed on single crystals both compounds are semiconductors. In contrast to the variable-range hopping of the transport mechanism of Co bearing material, the electrical resistivity of Ba₄Ru₂FeO₁₀ follows an activation law resulting in a band gap of approximately 0.98 eV.     

Configuration interaction in the 6s n d 1 D 2 and 6s n s 1 S 0 states of Yb probed by lifetime measurements

Radiative lifetimes in the even parity 6s n d ¹ D ₂ (n=6?13) and 6s n s ¹ S ₀ (n=8?14) level series of neutral Yb have been measured. In contrast to a monotonicn*³ behaviour which is expected in the absence of configuration interaction a drastic decrease of the lifetime data was observed in the vicinity of multiply excited states. In addition, for certain levels a strong increase of the lifetime values has been found which may be ascribed to destructive interference due to configuration mixing which can also affect the branching ratios of the radiative decay of these levels.     

Synthesis,characterization, and crystal structure of a new truly one-dimensional compound: PV2S10

PV₂S₁₀ was obtained by heating the elements in stoichiometric proportions at 490°C in evacuated Pyrex tubes. The crystal symmetry is monoclinic, space group $\text{P2}{}_1\text{c}$, with the unit cell parameters a = 12.734(8)Å, b = 7.349(7)Å, c = 23.662(4)Å, β = 95°22(1), V = 2205(4)ų, and Z = 8. The structure was solved from 2269 independant reflexions, and anisotropic least squares refinement gave R = 0.036 with 236 variables. The structure can be described as made of [V₂S₁₂] units forming endless chains themselves linked, two by two, by [PS₄] tetrahedra. In these units each vanadium is surrounded by eight sulfur atoms (mean d_VS = 2.459Å) arranged in a distorted bicapped triangular prism. Two of these prisms shared a rectangular face to form [V₂S₁₂] groups, in which intercationic distances implied vanadium-vanadium bonds (mean d_VV = 2.852(2)Å). Between the infinite double chains, only SS weak van der Waals' bonds exist. More than two thirds of the sulfur atoms are present as [SS]^?II pairs, (mean d_SS = 2.015Å); the rest are S^?II anions.     

Structure and properties of the CaFe2O4-type cobalt oxide CaCo2O4

The calcium cobalt oxide CaCo₂O₄ was synthesized for the first time and characterized from a powder X-ray diffraction study, measuring magnetic susceptibility, specific heat, electrical resistivity, and thermoelectric power. CaCo₂O₄ crystallizes in the CaFe₂O₄ (calcium ferrite)-type structure, consisting of an edge- and corner-shared CoO₆ octahedral network. The structure of CaCo₂O₄ belongs to an orthorhombic system (space group: Pnma) with lattice parameters, a=8.789(2) Å, b=2.9006(7) Å and c=10.282(3) Å. Curie-Weiss-like behavior in magnetic susceptibility with the nearly trivalent cobalt low-spin state (Co³⁺, 3d, S=0), semiconductor-like temperature dependence of resistivity (ρ=3×10⁻¹ Ω cm at 380 K) with dominant hopping conduction at low temperature, metallic-temperature-dependent large thermoelectric power (Seebeck coefficient: S=+147 μV/K at 380 K), and Schottky-type specific heat with a small Sommerfeld constant (γ=4.48(7) mJ/Co mol K²), were observed. These results suggest that the compound possesses a metallic electronic state with a small density of states at the Fermi level. The doped holes are localized at low temperatures due to disorder in the crystal. The carriers probably originate from slight off-stoichiometry of the phase. It was also found that S tends to increase even more beyond 380 K. The large S is possibly attributed to residual spin entropy and orbital degeneracy coupled with charges by strong electron correlation in the cobalt oxides.     

Synthesis of a d2 kagome lattice antiferromagnet, (CH3NH3)2NaV3F12

The ground-state of S = 1 kagome lattice antiferromagnets (KLAFs), in the presence of strong geometric frustration and the smallest integer spin, has the potential to host a range of non-trivial magnetic phases including a quantum spin liquid. The effect of local geometry and metal-ion electronic structure on the formation of these predicted phases remain unknown due to, in part, the lack of an ideal analyte. Herein, a kagome lattice compound, (CH₃NH₃)₂NaV₃F₁₂ (1-V), featuring a single distinct V³⁺ (d²) site in the R$\bar{3}$m space group, was synthesized hydrothermally. In this S = 1, d² system, the trivalent vanadium ions are tetragonally compressed due to Jahn–Teller distortion. The interlayer methylammonium cations show static positional disorder with three possible orientations. The negative Curie–Weiss temperature and dominant antiferromagnetic interactions make 1-V a candidate to study S = 1 KLAF physics. The frequency-dependence of ac magnetic susceptibility and the heat capacity results suggest that 1-V has a spin glass ground state. This freezing of the spin dynamics may be due to competing exchange interactions, structural imperfection arising from the static disorder of the interlayer methylammonium cations or the presence of ‘defect’-like spins.

A new d²-vanadium-based KLAF, (CH₃NH₃)₂NaV₃F₁₂, was synthesized hydrothermally and is a candidate to study S = 1 KLAF physics.     

C-Metallierte chirale Aloxide als d2- und d3-Reagenzien für die Synthese enantiomerenreiner Produkte (EPC-Synthese)

C-Metallated Chiral Alkoxides as d²–-and d³ -Regents for the Synthesis of Enantiomerically Pure Compounds (EPC-Synthesis) The chloroalcohols (S)-1 -chloro-2-propanol ( 1 ), (S)-1 -chloro-2-methyl-2-pentanol ( 4 ), (R)-3-chloro-2-methyl-1 -propanol ( 7 ), (R)-4-chloro-2-butanol ( 10 ), and (2R, 3R)- 4-chloro-3-methyl-2-butanol (14), really available from the esters of lactic, 3-hydroxy-2-methylpropanoic, and 3-hydroxybutanoic acid are subjected to sequential metallation first with BuLi (or MeMgCl) and then with lithium naphthalenide (or Li metal powder) to give solutions of the highly reactive C -metallated alkoxides 15, 22, 26, 27 , and 28 , respectively. - These chiral d²- and d³ -reagents may be added to aldehydes (non-diastereoselectively), ketones, and CO₂ to give 1, 3- or 1 4-dioles ( 18-21, 24, 29-33 ) or δ-lactones ( 35, 36 ). Thiolations with dibenzyl disulfide (→ 16, 34 ) and a deuteration (→ 17 , (S)-(1-²H)propan-2-ol) were also carried out. Independent synthesis of (S)-1-benzylthio-2-propanol ( 16 ) and comparison of the specific rotations establish that no loss enantiomeric purity occurs on the metallation route. The results described represent and extension of the applicability of simple chiral building blocks to EPC-synthesis.     

Lifetime measurements of the 2p 3d 3 D 1, 2, 3 0 and 2p 3d 1 P 1 0 levels in NII by beam-foil-laser spectroscopy

Accurate lifetimes measured by means of the cascade-free method based on laser excitation of a fast ion beam preexcited in a carbon foil are reported for four 2p 3d levels in NII. The lifetime results are: τ(2p 3d ³ D ₁ ⁰ )=0.209±0.007 ns, τ(2p 3d ³ D ₂ ⁰ )=0.219±0.007 ns, τ(2p 3d ³ D ₃ ⁰ )=0.217±0.005 ns, and τ(2p 3d ¹ P ₁ ⁰ )=0.410±0.017 ns. These results are compared to theoretical and experimental lifetimes reported previously.     

Die Termschemata derd 1- undd 2-Elektronensysteme in achtfach koordinierten Komplexverbindungen der SymmetrieD 4d

The Splitting of the energy levels of the freed ¹ andd ² ions in a field of eight ligands arranged in an Archimedean antiprism is calculated as a function of ligand field strength. If in the case ofd ² the field strength surpasses a certain value a¹ A ₁ term becomes the ground level instead of a³ E ₂ one. Thed ²-octocyano-complexes are diamagnetic as postulated by this; calculated and experimental spectra are in good agreement.     

Hyperfine structure in the configurations 4f 13 6s6p and 4f 125d6s 2 of TmI

The laser-atomic-beam spectroscopy has been used to make precise measurements of the hyperfine structure in transitions starting from metastable states of the configuration 4f ¹²5d6s ² in¹⁶⁹TmI. With the resulting experimental magnetic dipole hyperfine constantsA _J andA _J values from former investigations a parametric analysis of the hyperfine structure in the configurations 4f ¹³6s6p and 4f ¹²5d6s ² has been performed using wavefunctions from fine structure calculations. A comparison of theoretical and experimental hyperfine constants allowed a test of the reliability of the wave-functions used. The hyperfine parameters respectively hyperfine radial integrals determined from the analysis were compared with corresponding data from ab initio calculations for the ground configuration in TmI.