The collision cross sections for the fine-structure mixing of caesium 6P levels induced by collisions with potassium atoms

The cross section for the fine-structure excitation transfer Cs(6P _1/2) → Cs(6P _3/2), induced by collisions with the ground state potassium atoms, has been measured by resonant Doppler-free two-photon spectroscopy. The population densities of caesium 6P _J (J=1/2, 3/2) levels were probed by thermionic detection of the collisionally ionized caesium atoms from the Cs(6P _J ) → Cs(10S _1/2) excitation channel. The cross section for the transfer process at the temperatureT=503 K has been found to be σ(1/2 → 3/2)=45 Ų ± 20%. The result is compared with previously published experimental cross sections for fine-structure transfer in resonance states of other alkali elements perturbed by potassium and a thoeretical value of the Li(2P _J )-K system calculated in a simple approach.     

Fine structure excitation transfer between the potassium 42P states induced by collisions with caesium atoms

Applying diode-laser resonant fluorescence method, the cross sections for the excitation energy transfer of the collisional process K*(4² P _1/2)+Cs(6² S _1/2)?K*(4² P _3/2)+Cs(6² S _1/2) have been measured. The values we have obtained are σ(1/2→3/2)=77 Ų and σ(3/2→1/2)=48 Ų. These results complete the sequence of data for the fine-structure mixing of the first-resonance states of alkali atoms colliding with the ground-state caesium atoms.     

Perspectives of laser-chemical isotope separation of a long-lived fission product: cesium-135

The cesium isotope ¹³⁵Cs has an extremely long half-life (τ_1/2 = 2.3 · 10⁶ y) and its high water solubility leads to the anxiety of exudation to ground water during geological disposal. Such a LLFP ¹³⁵Cs would be converted into ¹³⁶Cs (Its half-life is 13.16 d and it becomes stable ¹³⁶Ba) by neutron capture reaction. However intermingling ¹³³Cs of which the natural abundance is 100% disturbs this nuclear converting reaction because ¹³³Cs also absorbs neutrons and produces ¹³⁵Cs again. For separating ¹³⁵Cs from other cesium isotopes, laser-chemical isotope separation (LCIS) is believed to be suitable mainly due to the light absorption and emission stability. Isotope separation of alkali metal ⁸⁵Rb/⁸⁷Rb was successfully achieved, showed 23.9 of head separation factor by LCIS. The measured isotope shift of Cs D₂ line is within the reach of available semiconductor lasers having emission line width of less than 1 MHz, which shows that the selective excitation of ¹³⁵Cs may turn to be possible. It is known that cesium excited to the 6²P_3/2 state may forms cesium hydride while ground-state cesium does not. Therefore if the lifetime of 6²P_3/2 state is sufficiently longer than the inverse rate of the chemical reaction, ¹³⁵Cs can be extracted as cesium hydride. Applicability of the Doppler-free two-photon absorption method for selective excitation and further evaluation on Rydberg states and ionization should be investigated.     

Phase states of Li(Na,K,Rb,Cs)/W/Mn/SiO<Subscript>2</Subscript> composite catalysts for oxidative coupling of methane

This survey analyzes the results of studies into Li(Na,K,Rb,Cs)/W/Mn/SiO₂ composites, which are used as catalysts for oxidative coupling of methane (OCM). The focus is on phase states. Our analysis shows that the SiO₂ matrix is an active constituent of the composites and not an inert carrier of additives and the OCM heterogeneous process involves alkali-metal tungstate melts, along with polycrystalline manganese oxides. The effects of the cation ratio and synthetic routes on the phase composition of Li(Na,K,Rb,Cs)/W/Mn/SiO₂ are assessed.     

Trigonal-prismatische Nb6-Einheiten in Verbindungen des Typs A3[Nb6SBr17] (A = Tl,K, Cs)

Trigonal-prismatic Nb₆-Units in Compounds of the Type A₃[Nb₆SBr₁₇] (A = Tl, K, Cs) The new compounds A₃[Nb₆SBr₁₇] (A = Tl, K, Cs) were synthesized and their lattice parameters were calculated from indexed X-ray powder patterns. An intensity measurement based on a single-crystal of Tl₃[Nb₆SBr₁₇] was performed with an automatic four-circle diffractometer (a = 1704.9(1) pm, b = 1862.8(3) pm, c = 932.51(7) pm; β = 90.747(7)°, V_m = 445.9(3) cm³/mol; C2/c, Z = 4). The structure refinement confirmed consistency with the Rb₃[Nb₆SBr₁₇] structure, found previously. The comparison of both structures yielded no significant differences concerning the distances within the sulfur-centered Nb₆S cluster core. Extended Hückel calculations revealed a maximum of the niobium–niobium overlap populations for (the actual present number of) 14 electrons occupying metal–metal bonding states.     

Theoretical electronic structure including spin–orbit effects of the alkali dimer cation

A theoretical study of the electronic structure of has been performed, including or not spin–orbit coupling. Potential energy curves for all the molecular states dissociating up to the limit Cs⁺ + Cs (8s ²S_1/2), i.e 26 states in the representation and 38 states in the representation Ω_g,u, are displayed. Equilibrium distances, transition energies and depths for the wells predicted at short and large range of internuclear separation R are reported. The existence of some of the long-range wells are confirmed by a long range model. Extensive tables of energy values versus internuclear distances are available at the following address: http://lasim.univ-lyon1.fr/allouche/cs2plus.htm.     

Plutonium isotopes and 137Cs in Dolon settlement near the Semipalatinsk Nuclear Test Site: About 50 years after the first nuclear weapon testing

Recent controversies concerning the radiation doses for populations living in the village of Dolon due to the nuclear explosions carried out at the Semipalatinsk Nuclear Test Site (SNTS) have encouraged us to evaluate in more detail the levels and distributions of residual long-lived radionuclides¹³⁷Cs and Pu isotopes (²³⁸Pu,^239,240Pu) in soils within the village. Soil core samples up to a depth of about 30 cm and/or 100 cm were collected at 25 sites and subjected to analysis of ¹³⁷Cs and Pu isotopes. The inventories of ¹³⁷Cs and ^239,240Pu were found to be in the wide range of 790-10,310 and 530-14,320 Bq/m², respectively. Sequential leaching of Pu from the soil showed that more than ca. 80% of the ^239,240Pu was not leached by hot digestion with conc. HNO³ + H₂O₂, indicating the presence of Pu associated with fused silicates. Further, the presence of hot-particles from the Pu contaminants by a-track radiography technique using CR-39 polycarbonate was confirmed in the soil, even at present, after about 50 years from the first nuclear weapon testing. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electronic structure and magnetic properties of TMRh12 clusters

We report an experimental study of energy pooling collisions involving Cs atoms in the 6P and 5D states. The 5D state was populated by a cw dye-laser tuned to the cesium dipole-forbidden transition 6S → 5D at 685.0 nm. The 6P state was populated by subsequent radiative relaxation of the 5D state. The 6P population density was determined from the absorption of a cw diode-laser probe beam. The population densities of the 5D state and the higher, by energy pooling excited states were determined by measuring the corresponding fluorescence intensities relative to the fluorescence intensity from the optically thin quasi-static wings of the cesium D ₂ line. The rate coefficient for the process Cs*(6P)+Cs*(6P)→Cs**(6D)+Cs(6S) is found to be (4.2±0.13)×10^?10 cm³ s^?1 at T=570 K. In addition, estimates of the rate coefficients for the processes Cs*(6P)+Cs*(5D)→Cs**(7D)+Cs(6S) and Cs*(5D)+ Cs*(5D)→Cs**(7F)+Cs(6S) are given.     

Theory of transition probability saturation for photodissociation of Cs2 and photoionization of the 5D 5/2 product atoms

Transition probability saturation has been used as a means of investigation of cesium photoionization via photodissociative states of Cs₂ around 550 nm. We present here a theoretical interpretation of the data obtained with polarized light. It allows for dispersion of the cross-sections due to the multi-level structure of the dissociated molecules and of the 5D _5/2 product atoms. Thehfs in 5D _5/2 is also taken into account. From best data fits we obtain determinations of the averaged cross-sections, free of uncertainty due to Cs or Cs₂ densities. The 5D _5/2 ionization cross-section agrees with theoretical prediction.     

The Large Second‐Harmonic Generation of LiCs2PO4 is caused by the Metal‐Cation‐Centered Groups

We evaluated the individual atom contributions to the second harmonic generation (SHG) coefficients of LiCs₂PO₄ (LCPO) by introducing the partial response functionals on the basis of first principles calculations. The SHG response of LCPO is dominated by the metal‐cation‐centered groups CsO₆ and LiO₄, not by the nonmetal‐cation‐centered groups PO₄ expected from the existing models and theories. The SHG coefficients of LCPO are determined mainly by the occupied orbitals O 2p and Cs 5p as well as by the unoccupied orbitals Cs 5d and Li 2p. For the SHG response of a material, the polarizable atomic orbitals of the occupied and the unoccupied states are both important.     

Interfaces between 8-hydroxyquinoline aluminum and cesium as affected by their deposition sequences

The electronic structures of tris(8-hydroxyquinoline) aluminum (Alq₃) deposited on clean or Cs pre-covered Ag substrates have been studied by ultraviolet photoelectron spectroscopy. Interface of Cs deposited on Alq₃ has also been prepared for comparison. For a low coverage of Cs on Ag, deposition of Alq₃ on top of the Cs cannot induce any new electronic features. The low work function of the Cs reduces the barrier height of electron injection at the Alq₃/Cs/Ag contact to 0.3 eV, as compared to 1.6 eV for the Alq₃/Ag contact. For high Cs coverage, the Cs may diffuse as neutral atoms and undergo oxidation into the Alq₃ layer and form a new gap state at 0.9 eV above the Alq₃ highest occupied state, which is the same as that of Cs deposited on the Alq₃.     

Synthesis,structure, and thermal properties of fluorinated cesium beta-diketonates

Four fluorinated cesium beta-diketonates, Cs(CF₃COCHCOCF₃) (Cs(hfac)), Cs(CF₃COCHCOCH₃) (Cs(tfac)), Cs(OH₂)((Me)₃CCOCHCOCF₃) (Cs(OH₂)(ptac)), and Cs(OH₂)(PhCOCHCOCF₃) (Cs(OH₂)(btfac)), were synthesized by interaction of the corresponding beta-diketone and Cs₂CO₃ in Et₂O. The formation of Сs(CF₃C(OH)₂CH₂C(OH)₂CF₃)(CF₃COO) or Cs(CF₃C(OH)₂CH₂COCH₃)(tfac) was shown to be dependent on the reaction conditions. The compounds were characterized by elemental analysis, single crystal X-ray diffraction, and TG/DTA analysis. All compounds have ionic structures organized into pseudo chains (in the case of Cs(hfac) and Cs(CF₃C(OH)₂CH₂COCH₃)(tfac)) or pseudo layers (in other cases). According to the TG data Cs(hfac), Cs(tfac), Cs(OH₂)(ptac,) and Cs(OH₂)(btfac) decompose in inert atmosphere within the temperature range 30–550?°C.     

Charge exchange of O2+ with Cs: spectroscopy and predissociation pathways for the Πg Rydberg states of O2

Electron capture by keV O₂⁺ (X₂Π_g) ions from Cs atoms yields predominantly the ¹Π_g and ³Π_g Rydberg states of O₂ which subsequently predissociate. Through the use oftranslational spectroscopy on the neutral product atoms, we have located a number of vibrational levels of these states and determined the dissociation channels. Furthermore we have observed competition between diabatic and adiabatic behaviour in the dissociating channels.     

Luminescence of cesium dicyanoaurate(I). Evidence for extended Au(I)Au(I) interactions in two dimensions

The luminescence of microcrystalline samples of Cs[Au(CN)₂] is reported and ascribed to planar AuAu interactions. Low-temperature measurements from 1.6 to 100 K of the luminescence decay rate of Cs[Au(CN)₂] for the band centered at 458 nm reveal the presence of at least two emitting levels separated by 46 cm⁻¹. A simple orbital model is proposed to account for the luminescence, and spin—orbit coupling is invoked to explain the splitting of the two lowest states. The analogies and differences between this luminescence and that observed for salts of Pt(CN)₄²⁻ are briefly discussed.     

Syntheses,Crystal Structures,and Optical and Magnetic Properties of Some CsLnCoQ3 Compounds (Ln = Tm and Yb,Q = S; Ln = Ho and Yb,Q = Se)

The four new compounds CsTmCoS₃, CsYbCoS₃, CsHoCoSe₃, and CsYbCoSe₃ have been synthesized at 1123 K. These black‐colored isostructural compounds crystallize in the KZrCuS₃ structure type with four formula units in space group Cmcm of the orthorhombic system. The structure of these compounds is composed of layers separated by Cs atoms. Because there are no Q–Q bonds, the formal oxidation states of Cs/Ln/Co/Q are 1+/3+/2+/2?, respectively. CsHoCoSe₃ shows paramagnetic behavior with μ_eff = 11.9(1) μ_B, whereas CsYbCoS₃ displays an antiferromagnetic‐like transition at ～2.7 K with μ_eff = 5.85(1) μ_B. Both CsYbCoS₃ and CsYbCoSe₃ exhibit optical band gaps in the near infrared region and broad absorption bands at lower energies.     

On the significance of radiation trapping in the inductively coupled plasma

On the basis of an intuitive argument and experimental evidence, the authors suggest that the populations of radiating states (³P₁,¹p_t) and metastable states (³P₂,³P₀) of atomic argon are collisionally equilibrated in the ICP discharge. A mechanism for allowing suprathermal populations to exist in the analytical region of the ICP is proposed based on the “trappin” of resonance radiation within the discharge boundaries. The possible consequences of this model are discussed.     

CsNb3Br7S: Synthese,Struktur und Bindungsverhältnisse

CsNb₃Br₇S: Synthesis, Structure, and Bonding States The reaction of NbBr₅ with Nb, Cs and S in a sealed Nb container affords CsNb₃Br₇S at 800°C (3 days). Further on isotypic compounds of the general formula ANb₃X₇Ch with A = Rb, Cs; X = Cl, Br and Ch = S, Se are obtained. CsNb₃Br₇S crystallizes monoclinic (space group P2₁/a, Z = 2), with the lattice parameters a = 707.4(2), b = 1 888.4(4), c = 994.1(2) pm and β = 98.59(2)°. The crystal structure contains Nb₃ clusters being linked by two additional Nb? Nb bonds to form infinite chains. Adjacent chains are bridged by Cs atoms in a cubeoctahedral coordination sphere of Br atoms. Similar with Nb₃Br₈ seven electrons occupy metal—metal bonding states.     

The Zintl Phase Cs7NaSi8 – From NMR Signal Line Shape Analysis and Quantum Mechanical Calculations to Chemical Bonding

Powder samples as well as red and transparent single crystals of the Zintl phase Cs₇NaSi₈ were synthesized and characterized by means of X‐ray diffraction and differential thermal analysis. Cs₇NaSi₈ was found to be isotypic to the recently reported phase Rb₇NaSi₈. It crystallizes in the Rb₇NaGe₈ structure type forming trigonal pyramidal Si₄^4– anions. Two unique environments of the cations are observed, a linear arrangement [Na(Si₄)₂]^7– with short Na–Si distances of 3.0 Å and a Cs2 atom coordinated by six Si₄^4– anions with long Cs–Si distances of 4.2 Å. The bonding situation was investigated by a combined application of ²⁹Si, ²³Na, and ¹³³Cs solid‐state NMR spectroscopy and quantum mechanical calculations of the NMR coupling parameters. In addition the electronic density of states (DOS), the electron localizability indicator (ELI) and the atomic charges using the QTAIM approach were studied. Good agreement of the calculated and experimental values of the NMR coupling parameters was obtained. An anisotropic bonding situation of the silicon atoms is indicated by the chemical shift anisotropy being similar to Rb₇NaSi₈. Confirmation is given by the observation of one lone‐pair‐like feature for each silicon atom and two types of two‐center Si–Si bonds using the ELI. Calculation and NMR spectroscopic determination of the ²³Na and ¹³³Cs electric field gradients prove anisotropies of the charge distribution around the cations. Due to the similar values for the Na atoms in M₇NaSi₈ (M = Rb, Cs) equal bonding situations can be concluded. The much larger anisotropy of the charge distribution of the Cs atoms can be addressed as the main difference to Rb₇NaSi₈.     

Complexing between orthoperiodic acid and periodate ion in nitric acid solutions

Preparative synthesis techniques have been developed for four complex salts (Rb[H₄IO₆ · H₅IO₆], Cs[H₄IO₆ · H₅IO₆], Cs[H₄IO₆ · H₅IO₆ · 0.5H₂O], and 2CsNO₃ · HNO₃ · H₅IO₆). In the Cs(Rb)NO₃-H₅IO₆-HNO₃-H₂O systems, the starting component ratios, temperature schedules, and solvent-evaporation (H₂O + HNO₃) parameters have been determined to ensure the crystallization of the said compounds in individual states. For complex 2CsNO₃ · HNO₃ · H₅IO₆, solid-phase synthesis has also been developed. Highly water-sensitive Cs[H₄IO₆ · H₅IO₆] in the presence of water vapor converts to Cs[H₄IO₆ · H₅IO₆ · 0.5H₂O].     

AB initio calculations and matrix ftir studies of the sulfur trioxide radical anion

The structures and vibrational frequencies of SO⁻₃ (C_3v) and SO⁻₂ (C_2v) have been calculated at the UHF SCF/3-21 + G¹ level. By cocondensation of Cs atoms and SO₃ in an Ar matrix the FTIR spectrum of Cs₄SO₃ has been measured. The molecule is proposed to have C_s symmetry with SO₃ binding to Cs in a bidentate fashion.