Spark source mass spectrometric calibration of the local vibrational mode absorption of carbon in gallium arsenide on arsenic sublattice sites

An appropriate calibration of the local vibrational mode absorption of carbon in GaAs on arsenic sublattice sites, C_As, at wavenumber 582 cm^–1 (77 K) is presented. Integrated absorptions I_α of C_As, the dominant acceptor in undoped monocrystalline GaAs, and calibrated carbon concentrations [C] were measured in single crystals using the methods FTIR and SSMS, respectively. A calibration factor f_C = [C]/I_α of (7.1 ± 0.2) × 10¹⁵ cm^–1 has been derived for 2.8 × 10¹⁴ cm^–3≤ [C] ≤ 1.4 × 10¹⁶ cm^–3 above a SSMS detection limit of [C]_DL≅ 1.4 × 10¹³ cm^–3. The carbon concentrations [C] = [C]_SSMS/RSC_C were calibrated with a relative sensitivity coefficient RSC_C = [C]_SSMS/ [C]_TRUE of 3.1 ± 0.1. CPAA was used as a reference method for [C]_CPAA≥ 4.4 × 10¹⁴ cm^–3 in order to approximate [C]_TRUE. Received: 15 December 1998 / Revised: 8 April 1999 / Accepted: 13 April 1999     

Spark source mass spectrometric assessment of boron and nitrogen concentrations in crystalline gallium arsenide

The residual or doped element concentration [E] in GaAs measured by SSMS is only accurate with respect to the relative sensitivity coefficient RSC_E. For a trace element concentration, the RSC_E = [E]_SSMS/[E]_TRUE is set to unity, if no reference material or method is available to approximate the concentration to the true value. For boron a relative sensitivity coefficient of RSC_B = 0.94 ± 0.08 was obtained using TI-IDMS as a reference method. RSC_N = 1 is used for nitrogen determinations. A boron and nitrogen detection limit of 4.4 × 10¹³ cm^–3 is achieved. SSMS was used as reference method to calibrate the FTIR factor f_E = [E] / I_α due to the integrated local vibrational mode absorption I_α of atomic boron and nitrogen in GaAs. A factor of f_B = (12.0 × 2.7) × 10¹⁶ cm^–1 (517 cm^–1) and f_N = (7.4 ± 0.1) × 10¹⁵ cm^–1 (472 cm^–1) was obtained for a boron and nine nitrogen containing GaAs samples at 77 K and 10 K, respectively. Received: 15 December 1998 / Revised: 8 April 1999 / Accepted: 13 April 1999     

Spark source mass spectrometric assessment of boron and nitrogen concentrations in crystalline gallium arsenide

The residual or doped element concentration [E] in GaAs measured by SSMS is only accurate with respect to the relative sensitivity coefficient RSC_E. For a trace element concentration, the RSC_E = [E]_SSMS/[E]_TRUE is set to unity, if no reference material or method is available to approximate the concentration to the true value. For boron a relative sensitivity coefficient of RSC_B = 0.94 ± 0.08 was obtained using TI-IDMS as a reference method. RSC_N = 1 is used for nitrogen determinations. A boron and nitrogen detection limit of 4.4 × 10¹³ cm^–3 is achieved. SSMS was used as reference method to calibrate the FTIR factor f_E = [E] / I_α due to the integrated local vibrational mode absorption I_α of atomic boron and nitrogen in GaAs. A factor of f_B = (12.0 × 2.7) × 10¹⁶ cm^–1 (517 cm^–1) and f_N = (7.4 ± 0.1) × 10¹⁵ cm^–1 (472 cm^–1) was obtained for a boron and nine nitrogen containing GaAs samples at 77 K and 10 K, respectively. Received: 15 December 1998 / Revised: 8 April 1999 / Accepted: 13 April 1999     

Polymerization of acrylamide with persulfate–thiomalic acid initiator

The redox system of potassium persulfate–thiomalic acid (I₁–I₂) was used to initiate the polymerization of acrylamide (M) in aqueous medium. For 20–30% conversion the rate equation is where R_p is the rate of polymerization. Activation energy is 8.34 kcal deg^?1 mole^?1 in the investigated range of temperature 25–45°C. M_n is directly proportional to [M] and inversely to [I₁]. The range of concentrations for which these observations hold at 35°C and pH 4.2 are [I₁] = (1.0–3.0) × 10^?3, [I₂] = (3.0–7.5) × 10^?3, and [M] = 5.0 × 10^?2–3.0 × 10^?1 mole/liter.     

Lateral thermal expansion of cellulose Iβ and IIII polymorphs

Measurements of the thermal expansion coefficients (TECs) of cellulose crystals in the lateral direction are reported. Oriented films of highly crystalline cellulose I_β and III_I were prepared and then investigated with X‐ray diffraction at specific temperatures from room temperature to 250 °C during the heating process. Cellulose I_β underwent a transition into the high‐temperature phase with the temperature increasing above 220–230 °C; cellulose III_I was transformed into cellulose I_β when the sample was heated above 200 °C. Therefore, the TECs of I_β and III_I below 200 °C were measured. For cellulose I_β, the TEC of the a axis increased linearly from room temperature at α_a = 4.3 × 10^?5 °C^?1 to 200 °C at α_a = 17.0 × 10^?5 °C^?1, but the TEC of the b axis was constant at α_b = 0.5 × 10^?5 °C^?1. Like cellulose I_β, cellulose III_I also showed an anisotropic thermal expansion in the lateral direction. The TECs of the a and b axes were α_a = 7.6 × 10^?5 °C^?1 and α_b = 0.8 × 10^?5 °C^?1. The anisotropic thermal expansion behaviors in the lateral direction for I_β and III_I were closely related to the intermolecular hydrogen‐bonding systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1095–1102, 2002     

Synthesis and Structure of the Novel Pentaselenidohexaarsenate(I,II) Cluster Anion [As6Se5]2−

Methanolothermal reaction of [MnCl₃(9‐ane‐N₃)] with As₂Se₃ at 150 °C in the presence of Cs₂CO₃ affords violet‐coloured [Mn(9‐ane‐N₃)₂]As₆Se₅ ( 1 ). Its novel tricyclic selenidoarsenate(I,II) anion [As₆Se₅]^2? contains two five‐membered [As₃As(Se)Se] rings that are symmetry‐related by a crystallographic C₂ axis passing through the common As^I‐As^I bond between their respective first two ring members. The adjacent As^I atoms in the individual rings are bridged by the Se atom of the third [As₄Se] ring.     

Kinetic studies of the reaction of C2H5 with O2 at 295 K

The reaction between C₂H₅ and O₂ at 295 K has been studied with a flow reactor sampled by a mass spectrometer. With helium as the carrier gas the rate coefficient was found to increase from (1.2 ± 0.3) × 10^?12 to (3.6 ± 0.9) × 10^?12 cm³/s as [He] was increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm^?3. The importance of has been determined from a knowledge of the initial C₂H₅ concentration together with a measurement of the C₂H₄ produced in reaction (5). F, the fraction of the C₂H₅ radicals removed by path (5), was found to decrease from 0.15 to 0.06 as [He] increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm^?3. The rate coefficient for reaction (5) was found to be independent of [He] and to have a value of (2.1 ± 0.5) × 10^?13 cm³/s. The variation in F reflects the fact that k_1b increases as [He] increases. These observations are taken as evidence for a direct mechanism for C₂H₄ production and a collision-stabilized route for C₂H₅O₂ formation. Calculations indicate that the high-pressure limit for reaction (1b) is ～4.4 × 10^?12 cm³/s and that in the polluted troposphere the branching ratio for reactions (1b) and (5) will be ～l20.     

Bis{[phthalocyaninato(2–)]arsenic(III)} tetradecaiodotetraarsenic(III)

Crystals of the novel title arsenic(III) phthalocyanine complex, [As(C₃₂H₁₆N₈)]₂[As₄I₁₄] or [(AsPc)⁺]₂·[As₄I₁₄]²⁻, where Pc is phthalocyaninate(2−), have been obtained by the reaction of pure powdered As with phthalo­nitrile under a stream of iodine vapour at 493 K. The crystals are built up of separate but interacting [AsPc]⁺ cations and [As₄I₁₂]²⁻ anions. The As atom of the [AsPc]⁺ unit is bonded to the four iso­indole N atoms of the Pc macrocycle and lies 0.743 (2) Å out of the plane defined by these four N atoms. The anionic part of the complex consists of AsI₃ and [AsI₄]⁻ units joined together into an [As₄I₁₄]²⁻ anion. The arrangement of the oppositely charged moieties, [AsPc]⁺ and [As₄I₁₄]²⁻, in the crystal is determined mainly by ionic attraction and by donor–acceptor interactions between the [AsPc]⁺ and [As₄I₁₄]²⁻ ions.     

Bis{[phthalocyaninato(2–)]arsenic(III)} octa­iodo­diarsenic(III)

Crystals of the novel title arsenic(III)–phthalocyanine complex, [As(C₃₂H₁₆N₈)]₂[As₂I₈] or [AsPc]₂[As₂I₈], where Pc is the phthalocyaninate(2−) macrocycle, have been obtained from the reaction of pure powdered arsenic with phthalonitrile under oxidizing conditions (iodine vapour) at 463 K. The crystals are formed by separate but inter­acting [AsPc]⁺ cations and centrosymmetric [As₂I₈]²⁻ anions. The As atom of the [AsPc]⁺ ion is bonded to the four isoindole N atoms of the Pc macrocycle and lies 0.762 (1) Å out of their plane. The anionic part of the complex consists of two [AsI₄]⁻ units joined together into a centrosymmetric [As₂I₈]²⁻ counter‐ion. The arrangement of oppositely charged moieties, viz. [AsPc]⁺ and [As₂I₈]²⁻, in the crystal structure is determined mainly by their ionic attractions and by π–π inter­actions between the aromatic phthalocyaninate(2−) macrocycles.     

Photoluminescence study of silicon solar cells irradiated with large fluence electrons or protons

In order to investigate the anomalous degradation of space silicon solar cells which was found in large fluence region, photoluminescence measurements are carried out for the cells irradiated with 1 MeV electrons with a fluence exceeding 1×10¹⁶ e/cm² and 10 MeV protons with a fluence exceeding 1×10¹³ p/cm². For both irradiation, the intensity of boron-related bound exiton line decreases with fluence and it disappears at the fluences where the anomalous degradation occurs. The dominant defect is a complex of an interstitial carbon and an interstitial oxygen (C_I–O_I). The generation of five-vacancy-defects was also observed for the proton irradiation. Variations of photoluminescence line intensity are discussed in terms of displacement damage dose calculated based on non-ionizing energy loss (NIEL).     

Precipitation polymerization of acrylamide using vazo-33 as an initiator and acetonitrile/water mixtures as the solvent

Precipitation polymerization of acrylamide initiated by a thermal initiator, Vazo-33 (DuPont Vazo Initiator), was achieved at a solvent composition of acetonitrile/water = 4/6 (vol/vol). The polymerization kinetics were investigated in the acrylamide [M] concentration range 0.86–2.27M, Vazo-33 [I] concentration range 1.4–11.0 × 10^?4M, and temperature range 30–40°C. Polymerization was carried out in reaction ampules and the rate was determined gravimetrically. Number-average molecular weight was obtained from intrinsic viscosity. The precipitation polymerization rate varied as [M]^2.16 and [I]^0.44. Number-average molecular weight was proportional to [M]^1.22 and inversely proportional to [I]^0.31. The overall reaction activation energy was calculated as 17.3 kcal/mol in the temperature range studied. The optimal reaction conditions studied were: acetonitrile/water = 4/6, temperature = 40°C, [M] = 1.95M and [I] = 2.8 × 10^?4M. One hundred percent conversion was achieved in 90 min and a polymer with a number-average molecular weight of 1,200,000 was obtained.     

Electroactive block copolymers

Synthesis, characterization and properties of microphase separated mixed (ionic and electronic) conducting or MIEC block copolymers are reported. Poly{[ω-methoxyocta(oxyethylene) methacrylate]-block-(4-vinylpyridine)}, abbreviated as P[MG8–4VP], and poly{(3-methylthiophene)-block-[(ω-methoxyocta(oxyethylene) methacrylate]}, abbreviated as P[3MT-MG8], have been synthesized. Differential scanning calorimetry (DSC) studies indicate that the polymers form a microphase separated structure. P[3MT-MG8] can be doped with I₂ and LiClO₄ to generate electronic and ionic conducting microdomains, respectively. For the P[3MT-MG8] series, bulk electronic conductivity as high as 1×10⁻³ S cm⁻¹ and bulk ionic conductivity as high as 6.6×10⁻⁷ S cm⁻¹ is observed at 30°C. This work represents a new concept in the area of electroactive polymers and should impact the microelectrochemical device industry.     

The crystal and molecular structure of ortho-terphenylenemercury dimer, (C18H12Hg)2

C₃₆H₂₄Hg₂, hexabenzo[b,d,f,i,k,m][1,8] dimercuracyclotetradecene, M_r = 857.768, monoclinic, P2₁/n, a 17.315(3), b 16.576(2), c 10.545(6) Å, β 114.60(4)°, U 2751.65 ų, Z = 4, D_m 2.055, D_x 2.071 g cm⁻³, λ(Mo-K_α) 0.71069 Å, μ 107.51 cm⁻¹, F(000) = 1600, T 293 K; Final R = 0.041 for 4290 observed reflections with I > 3σ(I). The two CHgC angles are 175.5(3) and 175.6(4)°; average CHg distance, 2.088(13) Å.     

A Tray‐Shaped,PdII‐Clipped Au3 Complex as a Scaffold for the Modular Assembly of [3×n] Au Ion Clusters

A tray‐shaped Pd^II₃Au^I₃ complex ( 1 ) is prepared from 3,5‐bis(3‐pyridyl)pyrazole by means of tricyclization with Au^I followed by Pd^II clipping. Tray 1 is an efficient scaffold for the modular assembly of [3×n] Au^I clusters. Treatment of 1 with the Au^I₃ tricyclic guest 2 in H₂O/CH₃CN (7:3) or H₂O results in the selective formation of a [3×2] cluster ( 1 ? 2 ) or a [3×3] cluster ( 1 ? 2 ? 1 ), respectively. Upon subsequent addition of Ag^I ions, these complexes are converted to an unprecedented Au₃–Au₃–Ag–Au₃–Au₃ metal ion cluster.     

Structural features of the phosphorus heterocumulene ylides (<Emphasis Type="Italic">sp</Emphasis>-ylides)

The features in phosphorus heterocumulene yilides Ph₃PCCX [X = NPh, NC(O)Ph, C(CN)CO · (OMe), O, S] with the ylide carbon geometry close to sp-hybridization are studied using ab initio methods. Estimation of structural parameters of a new member in the Ph₃PC^α=C^β=NC(O)Ph series on the B3LYP/6-31G(d,p) level and together with experimental data for related ylide (X = NPh) gave the following values: r(PC^α) 1.665 Å, r(C^α=C^β) 1.237 Å, ω(PC^αC^β) 145.2°. Nonvalent interactions of sp ^λ orbital of the ylide carbon atom bearing extra negative charge with coplanar π-electrons of the nearest C^β=N bond are found close to those of nitrogen lone pair with the C^α=C^β bond and leading to up to 10° nonlinearity of C^α-C^β=N triad of the phosphorus iminoketene ylides. Chemical nonequivalence of the PC^ipso bonds in the triphenylphosphonium fragment, relation of \(^1 J_{PC^\alpha } \) spin-spin coupling and antisymmetric bonding vibration ν^as(C=C=X) to the structure of the carbanion, and inductive hyperconjugative influence of atom (or group) X on the ylide carbon geometry are discussed.     

Kinetics of CH(X2Π) radical reactions with propane,isobutane and neopentane

Rate constants over the temperature range 298–689 K are reported for the reaction of CH(X²Π) radicals with C₃H₈, i-C₄H₁₀ and neo-C₅H₁₂. The CH radical was generated by multiphoton laser photolysis of CHBr₃ and its disappearance monitored by laser-induced fluorescence (LIF) at 429.8 nm. Absolute rate constants were determined as a function of temperature and total pressure. The following Arrhenius parameters were derived: k = (1.85 ± 0.13) × 10⁻¹⁰ exp[(240±30)/T] cm³/s for CH+propane; k = (2.03±0.19)×10⁻¹⁰ exp[(240±40)/T] cm³/s for CH+isobutane; k = (1.61±0.10)×10⁻¹⁰ exp[(340±30)/T] cm³/s for CH+neopentane, all independent of total pressure. The negative temperature dependences along with the energetics and lack of pressure effects lead to the conclusion that the reactions proceed by CH insertion into the alkane. The activated adduct thus formed rapidly decomposes via many energetically accessible channels. An analysis of CH reactions with C₁ to C₅ alkanes shows an increase in the room temperature rate constants in going from C₁ to C₄ irrespective of the nature of CH bonds. The rate constant then begins to level off near ≈ 5 × 10⁻¹⁰ cm/s for C₄ and C₅ alkanes.     

X‐ray diffraction study of the thermal expansion behavior of cellulose triacetate I

Highly crystalline samples of cellulose triacetate I (CTA I) were prepared from highly crystalline algal cellulose by heterogeneous acetylation. X‐ray diffraction of the prepared samples was carried out in a helium atmosphere at temperatures ranging from 20 to 250 °C. Changes in seven d‐spacings were observed with increasing temperature due to thermal expansion of the CTA I crystals. Unit cell parameters at specific temperatures were determined from these d‐spacings by the least squares method, and then thermal expansion coefficients (TECs) were calculated. The linear TECs of the a, b, and c axes were α_a = 19.3 × 10^?5 °C^?1, α_b = 0.3 × 10^?5 °C^?1 (T < 130 °C), α_b = ?2.5 × 10^?5 °C^?1 (T > 130 °C), and α_c = ?1.9 × 10^?5 °C^?1, respectively. The volume TEC was β = 15.6 × 10^?5 °C^?1, which is about 1.4 and 2.2 times greater than that of cellulose I_β and cellulose III_I, respectively. This large thermal expansion could occur because no hydrogen bonding exists in CTA I. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 517–523, 2009     

Structure and properties of 2-[(E)-2-(4-dipropylaminophenyl)-1-ethenyl]-1,3,3-trimethyl-3H-indolium chloride

The structure of styryl dye, 2-[(E)-2-(4-dipropylaminophenyl)-1-ethenyl]-1,3,3-trimethyl-3H-indolium chloride (I), was investigated using methods such as UV-VIS, fluorescence spectroscopy, and NMR (¹H, ¹³C, APT, HMQC, COSY) and also by examining its electrochemical properties. A study of the acid-base properties revealed the existence of three different forms of the dye. The mechanisms of protolysis and hydrolysis are discussed. The reagent exists in a reactive single-charged form I ⁺ over a wide range of acidity (pH 4–11). The optimum analytical wavelength of the singlecharged form is 550 nm, where the molar absorptivity is 5.51 × 10⁴ L mol^?1 cm^?1. The values of the optimum analytical wavelength and molar absorptivity of the protolysed and hydrolysed forms are: λ _max(I-H²⁺) = 380 nm, ?(I-H²⁺) = 2.01 × 10⁴ L mol^?1 cm^?1; λ _max(I-OH) = 320 nm, ?(I-OH) = 1.12 × 10⁴ L mol^?1 cm^?1. A theoretical study of the spectral and chemical properties of I was carried out by performing quantum chemical calculations.     

Rate constants for the reactions of C2H5O,i‐C3H7O,and n‐C3H7O with NO and O2 as a function of temperature

The rate constants of the reactions of ethoxy (C₂H₅O), i‐propoxy (i‐C₃H₇O) and n‐propoxy (n‐C₃H₇O) radicals with O₂ and NO have been measured as a function of temperature. Radicals have been generated by laser photolysis from the appropriate alkyl nitrite and have been detected by laser‐induced fluorescence. The following Arrhenius expressions have been determined: (R₁) C₂H₅O + O₂ → products k₁ = (2.4 ± 0.9) × 10⁻¹⁴ exp(−2.7 ± 1.0 kJmol⁻¹/RT) cm³ s⁻¹ 295K < T < 354K p = 100 Torr (R₂) i‐C₃H₇O + O₂ → products k₂ = (1.6 ± 0.2) × 10⁻¹⁴ exp(−2.2 ± 0.2 kJmol⁻¹/RT) cm³ s⁻¹ 288K < T < 364K p = 50–200 Torr (R₃) n‐C₃H₇O + O₂ → products k₃ = (2.5 ± 0.5) × 10⁻¹⁴ exp(−2.0 ± 0.5 kJmol⁻¹/RT) cm³ s⁻¹ 289K < T < 381K p = 30–100 Torr (R₄) C₂H₅O + NO → products k₄ = (2.0 ± 0.7) × 10⁻¹¹ exp(0.6 ± 0.4 kJmol⁻¹/RT) cm³ s⁻¹ 286K < T < 388K p = 30–500 Torr (R₅) i‐C₃H₇O + NO → products k₅ = (8.9 ± 0.2) × 10⁻¹² exp(3.3 ± 0.5 kJmol⁻¹/RT) cm³ s⁻¹ 286K < T < 389K p = 30–500 Torr (R₆) n‐C₃H₇O + NO → products k₆ = (1.2 ± 0.2) × 10⁻¹¹ exp(2.9 ± 0.4 kJmol⁻¹/RT) cm³s⁻¹ 289K < T < 380K p = 30–100 Torr All reactions have been found independent of total pressure between 30 and 500 Torr within the experimental error. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 860–866, 1999     

Iodination of cyclo‐E5‐Complexes (E=P,As)

In a high‐yield one‐pot synthesis, the reactions of [Cp*M(η⁵‐P₅)] (M=Fe ( 1 ), Ru ( 2 )) with I₂ resulted in the selective formation of [Cp*MP₆I₆]⁺ salts ( 3 , 4 ). The products comprise unprecedented all‐cis tripodal triphosphino‐cyclotriphosphine ligands. The iodination of [Cp*Fe(η⁵‐As₅)] ( 6 ) gave, in addition to [Fe(CH₃CN)₆]²⁺ salts of the rare [As₆I₈]^2? (in 7 ) and [As₄I₁₄]^2? (in 8 ) anions, the first di‐cationic Fe‐As triple decker complex [(Cp*Fe)₂(μ,η^5:5‐As₅)][As₆I₈] ( 9 ). In contrast, the iodination of [Cp*Ru(η⁵‐As₅)] ( 10 ) did not result in the full cleavage of the M?As bonds. Instead, a number of dinuclear complexes were obtained: [(Cp*Ru)₂(μ,η^5:5‐As₅)][As₆I₈]_0.5 ( 11 ) represents the first Ru‐As₅ triple decker complex, thus completing the series of monocationic complexes [(Cp^RM)₂(μ,η^5:5‐E₅)]⁺ (M=Fe, Ru; E=P, As). [(Cp*Ru)₂As₈I₆] ( 12 ) crystallizes as a racemic mixture of both enantiomers, while [(Cp*Ru)₂As₄I₄] ( 13 ) crystallizes as a symmetric and an asymmetric isomer and features a unique tetramer of {AsI} arsinidene units as a middle deck.