Accurate lifetime measurements of the 2p 3d 1 D 0 and 2p 3d 3 P 2 0 levels in N II with the beam-foil-laser method

We have obtained accurate values for the radiative lifetimes of the 2p 3d ¹ D ⁰ and 2p 3d ³ P ₂ ^o levels in NII by the cascade-free beam-foil-laser spectroscopy method. Our results are (2p 3d ¹ D ⁰)=0.346±0.012 ns and (2p 3d ³ P ₂ ^o )=0.457±0.020 ns. Comparison of these results with experimental and recent theoretical lifetimes reported previously is also made.Senior Research Associate of the Belgian FNRS     

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.     

The spin-allowed and spin-forbidden 5s 2 1 S 0-5s5p 1 P 1,3 P 1 transitions in strontium isoelectronic sequence

Relativistic multiconfiguration Dirac-Fock (MCDF) transition energies and oscillator strengths are determined for both the spin-allowed 5s ^{2 1} S ₀-5s5p ¹ P ₁ and the spin-forbidden 5s ^{2 1} S ₀-5s5p ³ P ₁ transitions in the strontium isoelectronic sequence. The modest relativistic configuration mixing to represent intravalence correlation is combined with a polarization model to account for valence-core electron correlations. The multiconfiguration Dirac-Fock calculations are performed in an average level scheme; however for neutral strontium and singly ionized yttrium a thorough comparison of the average and the optimal level schemes is presented. The average level scheme, though less accurate for the neutral end of the sequence, avoids the convergence problems encountered for highly ionized systems, where the 5s 5p ³ P ₁,¹ P ₁ states are raised owing to the collapse of the 4d _{3/2, 5/2} spin-orbitals in the isoelectronic sequence and, thus, allows us to extend our study to multiple charged ions (throughW ³⁶⁺). Since for such systems there is practically no difference between the results of the average and the optimal level versions of MCDF calculations, we believe that our average level predictions of ionization energies and oscillator strengths for states with total angular numberJ=0 andJ=1 are of comparable quality to those that could be obtained with an optimal level scheme.This study was supported by the Pedagogical Academy of Kraków Statutory Activity Grant No BS-29/91     

Lifetimes of the 4s4p 3 P 1 and 4s3d 1 D 2 states of Ca I

The lifetimes of the 4s4p ³ P ₁ and 4s3d ¹ D ₂ metastable states of Ca have been studied using the time-of-flight technique. Two kinds of observations were performed. First, the exponential decay of the fluorescence, using a (continuous) dc discharge for excitation and then the velocity distribution of the radiating atoms, using a pulsed discharge, were measured. From the combined results of these measurements the lifetimes were derived. The lifetimes of the 4s4p ³ P ₁ and 4s3d ¹ D ₂ states of Ca are determined to be 0.57±0.03 ms and 1.5±0.4 ms, respectively.     

Spectroscopy and kinetics of the 1P1 and 3P2 states of Hg 6s6p in xenon

The spectra and kinetics observed following excitation of Hg 6s6p(¹P₁) in xenon show the occurence of complex attachment and relaxation processes. The ¹P₁ attaches to Xe in termolecular collisions to produce HgXe E¹1, which emits a broad band with λ_max ≈ 2150 Å. Addition of krypton to Hg, Xe mixtures enhances the E-state emission by atom exchange with an HgKr^* complex. The E state also undergoes collisional deactivation by Xe, rate coefficient (1.75 ± 0.25) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, to generate ³P₂. However, the predominant route for ³P₂ formation is via collision of ¹P₁ with Xe, rate coefficient ≈ 4 × 10⁻¹² cm³ molecule⁻¹ s⁻¹. With [Xe] at 760 Torr, about 75% of the generated ³P₂ is attached in the form of the HgXe(C ³2) complex; lifetimes up to 600 μs have been observed. Two new emission bands occur when ³P₂ is prepared in xenon. A sharp feature, slightly blue-shifted from the forbidden ³P₂:¹S₀ line, results when ³P₂ and Xe approach on the D ³1 surface. The other band is broad with λ_max ≈ 2520 Å; the carrier is assigned to an HgXe₂(³2_u) complex. Rate coefficients for deactivation of ³P₂ to lower ³P_J states have been measured.     

Stark-mixing effect on the 6p 2 1 S 0−6p 2 3 P 2 transition in Pb I

The intensity of the 531.5 nm electric-field-quench radiation has been measured on a thermal beam of neutral Pb atoms in the metastable 6p ^{2 1} S ₀ state. The measurement yields a Stark-mixing amplitude for transition between the 6p ^{2 1} S ₀ and 6p ^{2 3} P ₂ states. Combining this result with available experimental data sets an upper limit for the 6p 7s ³ P ₁ → 6p ^{2 1} S ₀ transition probability:A _ki <1.79·10³ s ^?1. Calculations for the 6p 7s → 6p ² and 6p 8s → 6p ², as well as transition rates of forbidden lines inside 6p ² configuration of PbI are presented and compared with existing experimental data.     

Synthesis of the One-dimensional Compound (Ph4P)[In(P2Se6)] in a Ph4P+-Containing Selenophosphate Flux,and Structure of [In(P2Se6)2]5– – a Discrete Molecular Fragment of the [In(P2Se6)]nn– Chain

The reaction of one equivalent of In with a molten flux of (Ph₄P)₂Se₅ and P₂Se₅ (1 : 2), at 250 °C gave the (Ph₄P)[In(P₂Se₆)] ( I ). Stoichiometric elemental synthesis at 750 °C produced the Cs₅In(P₂Se₆)₂ ( II ). The thin, yellow crystals of ( I ), and the irregular, dark orange crystals of ( II ), appear to be air- and water-stable. Compound ( I ) crystallizes in the monoclinic space group C2/c (no. 15) and at 23 °C: a = 23.127(7) Å, b = 6.564(1) Å, c = 19.083(3) Å, β = 97.42(2)°, V = 2873(1) ų, Z = 4, final R/R_w = 4.4/5.2%. Compound ( II ) crystallizes in the tetragonal space group P4₂/m (no. 84) and at 23 °C: a = b = 13.886(1) Å, c = 7.597(2) Å, V = 1464.9(3) ų, Z = 2, final R/R_w = 3.9/5.1%. Compound ( I ) contains infinite [In(P₂Se₆)]_n^n– with a structure related to that of K₂FeP₂Se₆. Compound ( II ) contains the discrete [In(P₂Se₆)₂]^5– which can be viewed as a fragment of the [In(P₂Se₆)]_n^n– chain.     

Beiträge zur Chemie des Phosphors. 230. Hexaisopropyl-tetradecaphosphan(6), P14i-Pr6, und Hexaisopropyl-hexadecaphosphan(6), P16i-Pr6 — Bildung und 31P-NMR-spektroskopische Strukturbestimmung

Contributions to the Chemistry of Phosphorus. 230. Hexaisopropyltetradecaphosphane(6), P₁₄i-Pr₆, and Hexaisopropylhexadecaphosphane(6), P₁₆i-Pr₆ — Formation and Structural Determination by ³¹P-NMR Spectroscopy Hexaisopropyltetradecaphosphane(6) ( 1 ) and hexaiso-propylhexadecaphosphane(6) ( 2 ) are formed together with other isopropylpolycyclophosphanes by the reaction of i-PrPCl₂ with P₄ and magnesium and have been enriched to 30 mol% and 10 mol%, respectively. According to ³¹P-NMR spectroscopic investigations, the novel conjuncto-phosphane skeletons of 1 and 2 are the annelation products of a P₅ ring with a P₁₁(5) or a P₁₃(5) partial skeleton, respectively, joined by a common P₂ bridge. Thus, 1 is 4,5,6,10,12,14-hexaisopropylpentacyclo-[9.2.1.0^2,9 .0^3,7 .0^8,13]tetradecaphosphane and 2 is 5,6,7,11,14,15-hexaisopropylhexacyclo[7.7.0.0^2,13 .0^3,10 .0^4,8 .0^12,16]hexadecaphosphane. The phosphorus hydrides P₁₄H₁₆ and P₁₆H₆ have the same skeletal structures which are also intermediate stages in the formation of Hittorf's phosphorus.     

Radiative lifetime of the Te2 B0+u and A0+u states excited by a pulsed dye laser

A pulsed dye laser has been used to measure the radiative lifetimes and quenching rates of transitions of the B0⁺_u and A0⁺_u states of Te₂. The observed zero pressure lifetimes vary from 55 to 730 ns. The quenching rates vary from 0.9 × 10⁶ to 40 × 10⁶ s⁻¹ Torr⁻¹.     

The crystal and magnetic structures of Ca2NdRuO6, Ca2HoRuO6, and Sr2ErRuO6

The crystal structure of Sr₂ErRuO₆ has been refined from neutron powder diffraction data collected at room temperature; space group P2₁/n, A = 5.7626(2), B = 5.7681(2), C = 8.1489(2) Å, β = 90.19(1)°. The structure is that of a distorted perovskite with a 1:1 ordered arrangement of Ru⁵⁺ and Er³⁺ over the 6-coordinate sites. Data collected at 4.2 K show the presence of long range antiferromagnetic order involving both Ru⁵⁺ and Er³⁺. The temperature dependence of the sublattice magnetizations is described. The crystal structure of Ca₂NdRuO₆ is also that of a distored perovskite (P2₁/n, A = 5.5564(1), B = 5.8296(1), C = 8.0085(1) β = 90.19(1)°. The β = 90.07(1)°) with a random distribution of Ca²⁺ and Nd³⁺ on the A site and a 1:1 ordered arrangement of Ca²⁺ and Ru⁵⁺ on the 6-coordinate B sites. The Ru⁵⁺ sublattice is antiferromagnetic at 4.2 K but there is no evidence for magnetic ordering of the Nd³⁺ ions. Ca₂HoRuO₆ is also a distorted perovskite (P2₁/n, A = 5.4991(1), B = 5.7725(1), C = 7.9381(2), β = 90.18(1)° at 4.2 K) with a cation distribution best represented as Ca_1.46Ho_0.54[Ca_0.54Ho_0.46Ru]O₆. There is no ordering among the Ca³⁺ or Ho³⁺ ions on either the A or the B sites, but the Ca/Ho ions form a 1:1 ordered arrangement with Ru⁵⁺ on the B sites. At 4.2 K the Ru⁵⁺ ions adopt a Type I antiferromagnetic arrangement but there is no evidence of long range magnetic ordering among the Ho³⁺ ions.     

Intercombination decay of 3s3p 3 P 1 0 in MgI-like Ni and Cu

The intercombination transition 3s^{2 1}S₀ ?3s3p³P ₁ ⁰ in Ni¹⁶⁺ and Cu¹⁷⁺ has been studied by beam-foil spectroscopic methods. Decay curve analysis yields lifetime values of (12.0±1.0)ns and (8.8±0.6)ns for Ni and Cu in agreement with various predictions.     

Electron-impact excitation of the transition 1s 22s 22p 5(2 P 3 2/0 −2 P 1 2/0 ) of Mg IV

Effective collision strengths for electron-impact excitation of the ground state fine structure transition² P ₃ ^2/0 ?² P ₁ ^2/0 have been calculated by using theR-matrix method. Twelve lowest target states, represented by configuration interaction wavefunctions are included in the scattering calculations.M1 andE2 transition probabilities are also calculated by employing the Breit-Pauli Hamiltonian.     

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.     

Radiative lifetimes of the Rb(n 2 F)(n=6, 7, 8) states measured with the stepwise dipole-quadrupole excitation scheme

We report measurements of lifetimes of the Rb(n ² F)(n=6, 7, 8) states performed in a vapour cell. TheF-states were excited in a two-step sequence of an electric-dipole transition followed by an electric-quadrupole transition. Single photon counting was used for detection. The results are: (6² F)=171(4), (7² F)=262(15), (8² F)=387(12) (in ns). These lifetimes, have been compared with theoretical values given by different authors. An estimate of the cross sections for quenching due to collisions with ground-state Rb atoms is also given.This work was supported by the Polish Committee for Scientific Research under grant No. 2 2341 92 03     

Novel M(II)–Hg(II) coordination polymers generated from metal-containing building blocks M(2-pyrazinecarboxylate)2 · (H2O)2 (M=Cu, Ni, Co) and HgCl2

A new class of M(II)–Hg(II) (M=Cu(II), Co(II), Ni(II)) mixed-metal coordination polymers, Cu(2-pyrazinecarboxylate)₂HgCl₂ (4), [Co(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.61H₂O (5) and [Ni(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.77H₂O (6), have been prepared by self assembly of metal-containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂(M=Cu(II), Co(II), Ni(II)), with HgCl₂. Compounds 4–6 were characterized fully by IR, elemental analysis and single crystal X-ray diffraction. Compound 4 crystallized in the monoclinic space group C2/c, with a=17.916(5) Å, b=7.223(2) Å, c=13.335(4) Å, β=128.726(3)°, V=1346.2(6) ų, Z=4. It contains alternating Hg(II) and Cu(II) metal centers that are cross-linked by 2-pyrazinecarboxylate spacers and chlorine co-ligands to generate a unique three-dimensional Hg(II)–Cu(II) mixed metal framework. Compound 5 crystallized in the triclinic space group P , with a=6.3879(7) Å, b=6.6626(8) Å, c=13.2286(15) Å, α=96.339(2)°, β=91.590(2)°, γ=113.462(2)°, V=511.71(10) ų, Z=1. Compound 6 also crystallized in the triclinic space group P , with a=6.3543(8) Å, b=6.6194(8) Å, c=13.2801(16) Å, α=96.449(2)°, β=92.263(2)°, γ=113.541(2)°, V=506.67(11) ų, Z=1. Compounds 5 and 6 are isostructural and in the solid state the Hg(II)M(II)Hg(II) units are connected by Hg₂Cl₂ linkages to produce a novel M(II)–Hg(II) (M=Co(II), Ni(II)) zigzag mixed-metal chain, in which a new type of M–M′–M′–M array was observed. The metal containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂ (M=Cu(II), Co(II), Ni(II)), exhibit different connectivities to HgCl₂ depending on the metal cation contained within them.     

Crystal and Molecular Structure of Ph3P+-CH = CH-NHC6H3(2-O-)(4-NO2)

Treatment of [Ph₃P⁺-CH = CH-NHC₆H₃(2-OH)(4-NO₂)]Cl^- with ethanolic KOH leads to proton abstraction not from nitrogen, but from oxygen to give a betaine-type compound Ph₃P⁺-CH = CHNHC₆H₃ · (2-O^-)(4-NO₂). Its structure was proved by means of X-ray diffraction. The C = C distance [1.341(3) Å] unambiguously points to a double bond. Single crystals of the betaine are monoclinic, space group P2(1)/c; unit cell parameters: a 9.028(4), b 14.066(6), and c 18.799(10) Å; 90, 76.23(4), and 90°. The unit cell contains two dimers bound by strong inter- and intermolecular hydrogen bonds. Previously published IR and ¹H NMR data do not contradict the betaine structure of the compound obtained.     

Preparation,Crystal Structure,Vibrational Spectra,and Thermal Behavior of Tl2H2P2O6 and Tl4P2O6

The new thallium(I) salts, Tl₂H₂P₂O₆ ( 1 ) and Tl₄P₂O₆ ( 2 ), were prepared and structurally characterized by single‐crystal X‐ray diffraction. Compound 1 crystallizes in the monoclinic space group P2₁/c and compound 2 in the orthorhombic space group Pbca. Both structures feature channels occupied by the lone electron pairs of Tl⁺ cations. Furthermore, those are built up by discrete [H₂P₂O₆]^2– for compound 1 and [P₂O₆]^4– units for 2 in staggered conformation for the P₂O₆ skeleton and the thallium cations. In Tl₂H₂P₂O₆ ( 1 ) the hydrogen atoms of the [H₂P₂O₆]^2– ion are in a “trans‐trans” conformation. The O ··· H–O hydrogen bonds between the [H₂P₂O₆]^2– groups consolidate the structure 1 into a three‐dimensional network. FT‐IR/FIR and FT‐Raman spectra of the crystalline title compounds were recorded and a complete assignment for the P₂O₆^4– modes is proposed. The phase purity of 1 was verified by powder diffraction measurements.     

Experimental and theoretical cross sections for photoionization of metastable Xe*. (6s 3 P 2, 3 P 0) atoms near threshold

Using high resolution laser photoelectron spectrometry we have determined absolute cross sections σJ ₀ J ₁ and the electron angular distribution parameter for one photon ionization of metastable Xe^*(6s ³ P _J0, J ₀ = 2, 0) atoms to the resolved Xe₊ (² P _J1, J ₁ = 3/2, 1/2) ion states at several wavelengths near threshold. For comparison with the present and future experimental data we have calculated partial cross sections and ß-parameters for photoionization of Xe^*(6s ³ P _J0, J ₀ = 2, 0) and of the analogous alkali atom Cs(6s) over the photoelectron energy range (0–5) eV. We have used both a term-dependent Pauli-Fock (PF) approach and a configuration interaction method involving Pauli-Fock atomic orbitals (CIPF). Through the PF method we include relativistic effects on the atomic orbitals; the CIPF method was designed to take into account the important electron correlation effects which are found to be essential for obtaining good agreement between the theoretical and experimental results.     

Synthesis and Characterization of Copper Hexathiometadiphosphate Cu2P2S6

Copper hexathiometadiphosphate, Cu₂P₂S₆, was synthesized and characterized. Brick‐red copper hexathiometadiphosphate Cu₂P₂S₆ crystallizes in the tetragonal space group P4₂/mnm (no. 136) with a = b = 5.2565(7), c = 15.066(3) Å and V = 416.3(1) ų in a novel structure type. This is the first hexathiometadiphosphate, whose crystal structure is based on a slightly distorted cubic closest packing of sulfur atoms. 1/3 of the tetrahedral voids are occupied by Cu and P in an ordered fashion, thus resulting in a layered structure. The structural motif of layers composed of corner‐sharing CuS₄ tetrahedra (comparable to red HgI₂) that are separated by [P₂S₆]^2– anions orientated perpendicular to these layers, is rarely found in solid state chemistry. The compound is diamagnetic and shows negligible electronic conductivity. Electronic structure calculations and UV/Vis measurements point to a bandgap in the visible range and explain the red color of the compound. Additionally, the oxidation state +1 for Cu was confirmed by the electronic structure calculations. The thermal properties of Cu₂P₂S₆ were investigated by DTA.     

Tensor polarizability of cadmium atoms in the excited state (5s5p)3 P 1

The tensor polarizability of the (5s5p)³ P ₁ level of cadmium atoms in a vapour cell were measured using level crossing technique and opto-magnetic double resonance in parallel electric and magnetic fields. The value of the tensor polarizability obtained from the level crossings is: ₂=1.33±0.04 kHz/(kV/cm)² and from the double resonance is: ₂=1.27±0.06 kHz/(kV/cm)². These results were compared with previous theoretical and experimental data of other authors.This work was supported in part by the Committee for Scientific Research under grant No. 2 0226 91 01