Molecular beam chemiluminescence XI: kinetic and internal energy dependence of the NO + O3 → NO2*,→ NO23 reaction

Seeded supersonic NO beams were used to study the kinetic energy dependence of both the electronic (NO₂^*) and vibrational (NO₂³) chemiluminescence of the NO + O₃ reaction. In addition the electronic CL is found to be enhanced by raising the NO internal temperature. This is shown to be due to enhanced reactivity of the NO(²Π,_{$\text{3}\text{2}$}) fine structure component. By difference NO(²Π_{$\text{1}\text{2}$}) is concluded to yield predominantly groundstate NO₂³. The excitation function for NO₂^* formation from NO(²Π_{$\text{3}\text{2}$}) is of the form σ_{$\text{3}\text{2}$}(E) = C(E/E₀ - 1)ⁿ over the 3–6 kcal energy range where n = 2.4 ± 0.15, C = 0.163 Ų and E₀ = 3.2 ± 0.3 kcal/mole. Vibrational IR emission from NO₂³ has an energy dependence different from electronic NO₂^* emission, confirming that emitters are formed predominantly in distinct reaction channels rather than via a common precursor (either NO₂^* or NO₂³). The short wavelength cutoff of the CL spectra recorded at elevated collision energies E ? 15 kcal/mole corresponds to the total available energy. These and literature results are discussed in the light of general properties of the (generally unknown) ONO₃ potential energy surfaces. The formation of electronically excited NO₂^* rather than energetically preferred O₂ (¹ Δg) (Gauthier and Snelling) can be rationalized in terms of surface hopping near a known intersection of potential energy surfaces more easily than by vibronic interaction in the asymptotic NO₂ product.     

Structure cristalline du phosphatoantimonate K3Sb3P2O14

K₃Sb₃P₂O₁₄ crystallizes in the rhombohedral system, space group $\text{R}\text{3}\text{m}$ with a = 7.147(1) Å, c = 30.936(6) Å, Z = 3. The structure was determined from 701 reflections collected on a Nonius CAD4 automatic diffractometer with $\text{Mo}\text{K}\text{α}$ radiation. The final R index and the weighted R_w index are 0.033 and 0.042, respectively. The structure is built up from layers of SbO₆ octahedra and PO₄ tetrahedra sharing corners. The potassium ions are situated between the (Sb₃P₂O₁₄)^3? covalent layers.     

Phase equilibrium relations in the binary systems LiPO3CeP3O9 and NaPO3CeP3O9

The LiPO₃CeP₃O₉ and NaPO₃CeP₃O₉ systems have been investigated for the first time by DTA, X-ray diffraction, and infrared spectroscopy. Each system forms a single 1:1 compound. LiCe(PO₃)₄ melts in a peritectic reaction at 980°C. NaCe(PO₃)₄ melts incongruently, too, at 865°C. These compounds have a monoclinic unit cell with the parameters: a = 16.415(6), b = 7,042(6), c = 9.772(7)Å; β = 126.03(5)°; Z = 4; space group $\text{C}{}_2\text{c}$ for LiCe (PO₃)₄; and a = 9.981(4), b = 13.129(6), c = 7.226(5) Å, β = 89.93(4)°, Z = 4, space group $\text{P2}{}_1\text{n}$ for NaCe(PO₃)₄. It is established that both compounds are mixed polyphosphates with chain structure of the type |M^I_IM^III_II (PO₃)₄|_∞M^I_I: alkali metal, M^III_II: rare earth.     

Nd3+, Eu3+, and Gd3+ ions as local probes in the NaxSr3−2xLnx(PO4)2 and KCaLn(PO4)2 rare earth phosphates

Use of Nd³⁺, Eu³⁺, and Gd³⁺ as local structural probes allows the determination of the rare earth positions in the Na_xSr_3?2xLn_x(PO₄)₂ (Ln = La to Tb) and KCaLn(PO₄)₂ phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and ${}^6\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels of the Gd³⁺ ions.     

Über Ordnungs-Unordnungsphänomene bei Sauerstoff perowskiten vom Typ A2+3B2+M5+2O9

Perovskites of the type A²⁺₃B²⁺M⁵⁺₂O₉, where A²⁺ = Ba, Sr; B²⁺ = Mn, Co, Ni, Zn; M⁵⁺ = Nb, Ta, show order-disorder phenomena. At lower temperatures a thermodynamically unstable disordered cubic perovskite is formed ($\text{1}\text{3}$ formula unit—$\text{AB}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{M}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{O}{}_3$—in the cell), which transforms irreversibly into a 1: 2 ordered high-temperature form with 3L structure (sequence (c)₃). For A²⁺ = Ba this lattice is hexagonal (space group $\text{P}\text{3}\text{m1}$; one formula unit in the cell); with A²⁺ = Sr a triclinic distortion is observed. For Ba₃CoNb₂O₉ a second transformation into a cubic disordered perovskite takes place at 1500°C. This transition is reversible and of the order-disorder type. The vibrational and diffuse reflectance spectra are discussed.     

Structure cristalline du composé RbEu3F10

Crystals of RbEu₃F₁₀ are cubic with a = 11.844 Å, Z = 8, and three possible space groups, $\text{Fm3m, F}\text{4}\text{3m}$, and F432. The structure has been resolved from three-dimensional X-ray data and refined by the least-squares method. The final R values are, respectively, 0.065 and 0.067 for Fm3m and $\text{F}\text{4}\text{3m}$, and are not significantly different. The rare earth symmetry is C_4v for Fm3m and C_2v for $\text{F}\text{4}\text{3m}$. Consequently, we have used the Eu³⁺ ion in the RbEu₃F₁₀ phase as a structural probe in order to state precisely the symmetry of the lanthanide site and distinguish among the possible space groups.     

Neutron powder diffraction and magnetic measurements on TlMnI3 and TlFeI3

TlMnI₃ and TlFeI₃ are isostructural with NH₄CdCl₃. TlMnI₃ has a spiral structure which can be described with an incommensurable vector k, in the direction of the b1 axis of length 0.3614(5)b1. The spins lie in the (0 0 1) plane. TlMnI₃ exhibits antiferromagnetic behavior with a Néel temperature of 6.0(2) K. The exchange interaction was calculated to be $\text{zJ}\text{k}\text{= ?1.6}\text{K}\text{, z}$ being the number of nearest neighbors. Discontinuities in the magnetization are found for both the [1 0 0] and [0 1 0] directions at fields H^a_SF = 30.1(2) kOe and H^b_SF = 14.1(2) kOe. The magnetic structure of TlFeI₃ consists of puckered ferromagnetic (1 0 0) planes, which are coupled antiferromagnetically. The magnetic moments are parallel to the b axis. The Néel temperature is 21.5(3) K. $\text{zJ}\text{k}$ was found to be ?10(1) K with g = 2.68 and s = 2. The magnetic structures found for TlMnI₃ and TlFeI₃ are derived taking into account inter- and intra-double-chain interactions via two I^? ions.     

Synthesis of triphenylphosphonopropionbetainetriorganotin(IV) salts [(C6H5)3P(CH2)2CO2SnR3]+X−, by nucleophilic displacement of anions from triorganotins

Trimethyl- and triphenyl-tin(IV) hydroxide act on triphenyl(2-carboxyethyl)-phosphonium hydrochloride, which is made from 3-chloropropionic acid and triphenylphosphine, to release water in the presence of dimethylformamide (DMF) as a catalyst. The water is azeotropically distilled to drive the reaction forward and produce triphenylphosphonopropionbetainetrimethyl- and triphenyl-tin(IV) chlorides in high yield. The latter product also results from the displacement of chloride from triphenyltin(IV) chloride by the phosphobetaine, (C₆H₅)₃P(CH₂)₂CO₂, which is made by treating the phosphonium hydrochloride with bicarbonate, and the compounds [(C₆H₅)₃P(CH₂)₂CO₂Sn(C₆H₅)₃]⁺X^? where X = Cl, Br, I, N₃, NCS, NO₃, B(C₆H₅)₄ and Co(CO)₄ are made in the same way. The acetate salt results from metathesis from the chloride and lead(II) acetate. A double salt, [(C₆H₅)₃P(CH₂)₂CO₂SnR₃]⁺ [R₃SnX₂]^?, is formed for X = Cl, Br and N₃ by adding additional (C₆H₅)₃SnX to the already-formed simple salts. Double salts are also obtained from the $\text{1}\text{1}$ reactions between the phosphobetaine and triphenyltin(IV) isocyanate and methyldiphenyltin(IV) chloride. The phosphonium chloride double salt could be converted to the thiophosphonium derivative by heating with elemental sulfur in ethanol. The products of these novel nucleophilic displacement reactions are high melting solids. Tin-119m Mössbauer data are consistent with five-coordinated, triorganotin(IV) formulations with the exception of the diphenyl(8-hydroxyquinolinato)tin(IV) chloride salt in which the tin atom is six-coordinated, and the diphenyltin system cis-oriented. The parameters otherwise do not change with the nature of the X group, which is the tetracarbonylcobaltate derivative is tetrahedral by infrared, establishing the ionicity of the products. The chloride exhibits a molar conductivity indicative of a $\text{1}\text{1}$ electrolyte in DMF. A bridging acetate structure in the solid is consistent with the lowered ν(CO₂) frequencies. The Mössbauer spectra of the double salts give simple doublets of lowered isomer shift (IS) and raised quadrupole splitting (QS) which may arise from a cross-linking ion pairing of the polymer chains in the solid, and the NMR spectra of the two methyltin derivatives shows only a single resonance line and tin satellites which is rationalized by a dynamic exchange process. The products are formulated as associated in carboxylate polymers with dangling triphenylphosphonium cations.     

The reaction of trihydrobistriphenylphosphine iridium IrH3(PPh3)2 with diazonium salts

The reaction of IrH₃(PPh₃)₂ with p-substituted aryldiazonium salts gives the compounds [IrH₂(NHNC₆H₄R)(PPh₃)₂]⁺BF₄^- at low temperature (-10°C) and the o-metalated complexes [I$\text{rH(NHN}$C₆H₃R)(PPh₃)₂]⁺BF₄^- (R  F, OCH₃) at 40–50°C. The reactions of the o-metalated complexes with CO, PPh₃, NaI and HCl have been studied.     

A pentagonal tunnel structure with copper in square planar coordination: The oxides KCuNb3O9 and KCuTa3O9

The structure of two new oxides KCuTa₃O₉ and KCuNb₃O₉ has been solved from X-ray powder data and by electron microscopy. Both compounds are orthorhombic, space group Pnc2 with $\text{a ? 8.8}$ Å, $\text{b ? 10.1}$ Å, and $\text{c ? 7.6}$ Å. Their host lattice is built up from corner-sharing MO₆ octahedra (M = Nb, Ta) forming pentagonal tunnels where the K⁺ ions are located. The copper ions are located in distorted perovskite CaCu₃Mn₄O₁₂-type cages and exhibit a square planar coordination. The relationships between these oxides and the TTB, HTB, ITB, and Ba_0.15WO₃ structures are discussed.     

ESR studies on the reactions of sulphite radical anion,SO3.̄−, with nitroalkane compounds in aqueous solutions

The reactions of the sulphite radical anion, SO₃^{$\text{.}\text{?}$?} (generated from the Ti³⁺-H₂O₂-Na₂SO₃ system at pH 9), in aqueous solutions with some nitroalkane compounds were investigated by using a rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 ms. The SO₃^{$\text{.}\text{?}$?} radical added to the double bond of CN in the nitroalkane aci-anions which are the main form of nitroalkanes in aqueous alkaline solutions. From the observed hyperfine splitting constants of the SO₃^{$\text{.}\text{?}$?} adducts of nitroalkane aci-anions, the preferred conformation of the adducts was deduced.     

Laser-induced fluorescence of high-temperature vapor complexes of ErCl3 with AlCl3, GaCl3 and InCl3

Laser excitation of equilibrium vapor mixtures ErCl₃(s)-ACl₃(g) (A = Al, Ga, In) at 475–1100 K gives rise both to resonance fluorescence from the f → f Er³⁺ transitions of the Er-Cl-A vapor complexes, and to Raman scattering due to the vibrational modes of the ACl₃ vapor. The laser-induced fluorescence from the ⁴F_{$\text{9}\text{2}$}, ⁴S_{$\text{3}\text{2}$} and ²H_{$\text{11}\text{2}$} states has been investigated at different temperatures and excitation.     

H3N·PF5 and H2NPF5−, new compounds in the system H3N/PF5

Phosphorus pentafluoride was reported long ago to give adducts 2 PF₅ ·5 NH₃ (1) and nNH₃·PF₅ (n= 1 ? 4) (2). None of the compounds was characterised in detail. Repeating the reaction of PF₅ and NH₃ we found the adduct H₃N·PF₅, $\text{1}$, in 8% yield besides (H₂N) ₂PF₃ (3) and NH₄PF₆. However, HF and (F₂P=N)₃ gave $\text{1}$ in 41% yield. The ¹H, ¹⁹F, and ³¹P n.m.r. spectra of $\text{1}$ exhibit ¹⁴NH, ¹⁴NPF(cis), and ¹⁴NP coupling. The x-ray structure determination shows almost perfect octahedral geometry at phosphorus with a PN bond length of 1.842 ā. Compound $\text{1}$ is soluble in water without decomposition. Treatment with NH₃ leads to the anion H₂NPF₅^?. Upon heating $\text{1}$ forms in good yield H₂NPF₄ and NH₄PF₆. Without a solvent $\text{1}$ and NH₃ react to give (H₂N) ₂PF₃. A mechanism for the ammonolysis of PF₅ is proposed.     

NMR study of hydrogen molybdenum bronzes: H1.71MoO3 and H0.36MoO3

Proton NMR relaxation times (T₂T₁, and T_1?) and absorption spectra are reported for the compounds H_1.71MoO₃ (red monoclinic) and H_0.36MoO₃ (blue orthorhombic) in the temperature range 77 K < T < 450 K. Rigid lattice dipolar spectra show that both compounds contain proton pairs, as OH₂ groups coordinated to Mo atoms in H_1.71MoO₃ and as pairs of OH groups in H_0.36MoO₃. The room temperature lineshape for H_1.71MoO₃ shows that the average chemical shielding tensor has a total anisotropy of 20.1 ppm. The relaxation measurements confirm that hydrogen diffusion occurs and give E_A = 22 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 10}{}^{\mathrm{?13}}\text{sec}$ for H_1.71MoO₃ and E_A = 11 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 3 × 10}{}^{\mathrm{?8}}\text{sec}$ for H_0.36MoO₃.     

Kinetic spectroscopy in the far vacuum ultraviolet. Part I: Detection of (2p5) 2P32,12 fluorine atoms using atomic resonance spectrometry in the wavelength range 95–98 nm

A new experimental system for atomic resonance spectrometry at λ < 105 nm in a discharge-flow system is described. The spectrum of a fluorine resonance lamp has been studied, and possible precursors for the 2p⁴ 3s excited F atoms formed are suggested. Ground state (2p⁵²P_{$\text{3}\text{2}$}) and J-excited ²P_{$\text{1}\text{2}$} F atoms have been detected for the first time in resonance absorption and fluorescence using the first resonance transitions with wavelengths between 95.2 and 97.8 nm. Preliminary measurements (using both ⁴P-²P and ²P-²P lines) of the variations with concentration of absorption intensity by ground state F ²P_{$\text{3}\text{2}$} and by J-excited F ²P_{$\text{1}\text{2}$} atoms are reported; F atom concentrations were measured using a titration method based on the rapid reaction, F + Cl₂ → FCl + Cl.     

Diffusion of oxide ions in LaFeO3 single crystal

The tracer diffusion coefficient, $\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$, of oxide ions in LaFeO₃ single crystal was determined over the temperature range of 900–1100°C by the gas-solid isotopic exchange technique using ¹⁸O as a tracer. For the determination of $\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$, the depth profile of ¹⁸O was measured by means of a secondary ion mass spectrometer (SIMS). The surface exchange reaction was found to be slow and the surface exchange rate constant, k, was determined together with $\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$. It was found that $\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$ at 950°C is proportional to P^?0.58_O2, where P_O2 is an oxygen pressure. The vacancy mechanism was determined for the diffusion of oxide ions from the P_O2 dependence. The vacancy diffusion coefficient, D_V, for LaFeO₃ was nearly the same as that for LaCoO₃ at the same temperature. The activation energy for migration of oxide ion vacancies was 74 kJ · mole^?1 for both oxides.     

1-methyl-(D3)-trishomocubane

The acid catalysed rearrangement of 8-methyl-pentacyclo(5.4.0.0^2,6.0^3,10.0^5,9)undecan-8-endo-o1 ($\text{8}$) to 3-methyl-(D₃)-trishomocuban-4-o1 ($\text{9}$) provided the key step to the synthesis of the title compound ($\text{11}$).     

Rare gas molecular ions: Formation of XeF+ by ion-molecule reactions in Xe and NF3 and evidence for radiative deactivation of Xe+ (2P12)

The formation of the XeF⁺ ion by ion-molecule reaction has been observed in an ionized mixture of Xe and NF₃ by ion cyclotron resonance mass spectrometry. The excited ²P_{$\text{1}\text{2}$} state of the xenon ion has unambiguously been identified as the major precursor by photoionization mass spectrometry. The NF⁺₃ ion makes an additional minor contribution. Evidence suggests that the excited ²P_{$\text{1}\text{2}$} xenon ion radiatively decays to the ²P_{$\text{3}\text{2}$} ground state on the time scale of the experiment. The transition probability deduced for this dipole forbidden emission, 18 ± 4 s^?1, is in good agreement with the theoretical value of 21 s^?1 for the sum of the magnetic dipole and electric quadrupole transition rates.     

Symmetry constraints in energy transfer between state-selected Ar*(3P2, 3P0) metastable atoms and ground state H atoms

The excitation-transfer reaction in thermal energy collisions of state-selected metastable Ar*(³P₂) and Ar*(³P₀) atoms with ground state H atoms, giving excited H*(n = 2) atoms, has been studied with the stationary afterglow technique. The rate constant for the excitation of H atoms by Ar*(³P₂) has been found to be more than one order of magnitude larger than in excitation by Ar*(³P₀). This difference in the reactivity of two metastable species is explained to be a consequence of the attractive nature of the D(²II) and E(²Σ⁺) potentials that develop from the Ar*(³P₂)+H entrance channel and which give curve crossing with the B(²II) and C(²Σ⁺ potentials, respectively, leading to the Ar+H*(n=2) exit channel, whereas only a repulsive ⁴II (Ω=$\text{1}\text{2}$) potential develops from the Ar*(³P₀+H entrance channel.