CO2Laser Photochemical Hole Burning in the IR Reflection Spectra of Crystalline Natural Silicates

Structural and chemical transformations induced on the surface of crystalline natural silicates by pulse ₂laser radiation with a pulse length of 200 ns and an energy per pulse of 2 J were examined. The IR reflection spectra of nepheline KNa₃[AlSiO₄]₄and rhodonite CaMn₄[Si₅O₁₅] were measured before and after exposure to laser radiation. An increase in the reflectance at the laser frequency used was observed, which was named hole burning in the IR reflection spectra of specimens. A 50-cm^–1wide hole was shown to be burnt at a frequency coinciding with that of a laser radiation line within this width. At the incident laser frequency, a narrow, 5-cm^–1wide hole is also burnt in the IR spectra of the irradiated samples. The burning of the 50-cm^–1hole was assumed to be due to the selective sublimation of Si_mO_ncomplexes. The burning of the narrow hole of 5 cm^–1width is associated with the laser-induced selective dissociation of Si–O bonds in the near-surface layer at the frequency employed.     

Flame Atomic Absorption Spectrometric Determination of Gold and Palladium Using Microcolumn On-line Preconcentration and Separation

A microcolumn on-line preconcentration and separation system was developed for the flame atomic absorption spectrometric (FAAS) determination of trace levels of gold and palladium. The analytes were selectively adsorbed onto the microcolumn packed with 2-mercaptothiazole immobilized silica gel (MBTSG) in an acidity range of 0.1 to 6.0M HCl at a sampling flow rate of 4.0mLmin^–1. The analytes adsorbed could be desorbed by a thiourea solution with a flow rate of 2.0mLmin^–1. Most of the common coexisting metal ions at a concentration of 25.0mgmL^–1 and anions at a concentration of 50.0mgmL^–1 did not interfere with the preconcentration and determination of Au and Pd. The limits of detection (LOD), defined as three times the standard deviation of the blank (3), of Au and Pd are 10ngmL^–1 and 26ngmL^–1, respectively, with a preconcentration time of 60s. The relative standard deviation (RSD) is about 2.0% for 0.20µgmL^–1 Au and 0.30µgmL^–1 Pd. With a sample loading time of 30min, 6.7ngmL^–1 Au and 10ngmL^–1 Pd can be preconcentrated quantitatively. A geological sample, an anode slime and a secondary nickel alloy were successfully determined with the proposed method, and the results obtained showed good agreement with the certified values.Received December 23, 2002; accepted May 14, 2003 Published online August 8, 2003     

Infrared spectral analysis during the thermal decomposition of pure and irradiated crystalline NH4ClO4

Variable temperature /303–553 K/ IR spectroscopic studies are made during thermal decomposition of pure and -treated ammonium perchlorate /AP/. Decomposition is enhanced by radiation or in the presence of an additive /Gd₂O₃/. Intensity of the stretching /1100 cm^–1/ and bending /625 cm^–1/ frequencies of ClO ₄ ^– decrease on heating the KBr matrix even below 360 K. Above this temperature, a broad band develops over 480–510 cm^–1 in the pure and -treated AP which is attributed to ClO ₃ ^– /₄/.     

Multiphoton dissociation of C3F6O

Major characteristics of multiphoton absorption and multiphoton dissociation of hexafluoropropene oxide (HFPO) were studied. Spectral relationships of the average number of IR photons absorbed per molecule and the yield of multiphoton dissociation were determined in the range of 1040-985 cm^–1 at different laser fluences. At the laser line 1025.3 cm^–1, the effect of collisions with buffer gases on the HFPO multiphoton absorption and multiphoton dissociation was studied and theq-factor was determined (q = O.6 at= 0.55J cm^–2). Characteristic features of HFPO decomposition under collisional conditions (p _HFPO> 0.1 Torr) were discussed. An anomalous difference in the values for quantum efficiency of multiphoton dissociation for long-wave and short-wave wings of HFPO absorption band was revealed. A procedure for correlating the experimental and theoretical data on the yield of multiphoton dissociation (when theq-factor is unknown) was suggested, and corresponding calculations were performed for the frequency 989.6 cm^–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1927–1932, November, 1994.     

Diffuse-Reflectance IR Spectra of Methane Adsorbed on NaZSM-5 and HZSM-5 Zeolites

Diffuse-reflectance IR spectra of methane adsorbed on high-silica NaZSM-5 and HZSM-5 zeolites point to a stronger adsorption of methane on sodium cations than on protons. For the asymmetric stretching vibration ₃, this form of adsorption is characterized by a doublet with band maxima at 2980 and 3010 cm^–1. For the fully symmetric stretching vibration ₁, it is characterized by a singlet with a maximum at 2880 cm^–1. Methane is also adsorbed on NaZSM-5 in a weaker form, which is characterized by absorption bands with maxima at 3002 (₃) and 2887 (₁) cm^–1. The weaker form of methane adsorption on acidic bridging hydroxy groups of HZSM-5 is characterized by absorption bands at 3001 and 2887 cm^–1 (₃ and ₁, respectively). A difference between this form of adsorption and weak adsorption on sodium-exchanged zeolite reveals itself in the somewhat higher intensity of the band at 2887 cm^–1. For methane adsorbed on NaZSM-5, the frequencies of deformational vibrations and a spectrum in the near IR region are obtained for the first time. It was found that the perturbance of adsorbed methane molecules is seen in the spectrum as in the low-frequency shifts of most of the bands that appear due to composite vibrations and overtones and as new adsorption bands that were not observed for gaseous methane.     

Solvent extraction and spectrophotometric including graphite furnace atomic absorption determination of molybdenum in the environment

A selective and sensitive method for the extraction and microgram determination of molybdenum (VI) with hydroxamic acid as yellow molybdenum-hydroxamate complex from acidic medium is described. The molybdenum-PCPPSAHA complex has _max 388 nm, molar absorptivity 5.0 × 10³l mol^–1 cm^–1. The system obeys Beer's law in the range of 1–28 g/ml of molybdenum(VI). Sandell's sensitivity is 0.0192 g cm² and stoichiometry of the complex is 12, molybdenum: PCPPSAHA while mixed complex molybdenum-PCPPSAHA-morin has _max 400 nm and molar absorptivity 5.9 × 10³lmo1^–1 cm^–1 and stoichiometry of the complex is 121.The molybdenum is determined by graphite furnace atomic absorption spectrophotometry after directly pipetted the extract into the furnace which increases the sensitivity 20 fold.     

Overton-Region IR Registration of (≡Si–O)2Si=O and (≡Si–O)2Si〈O2〉C=O Groups on the Silica Surface

IR spectroscopy in a range of 2050–4000 cm^–1 (the range of overtones and composite frequencies) is used to study the groups (Si–O)₂Si=O and (Si–O)₂SiO₂C=O with different isotopic compositions (¹⁶O, ¹⁸O, ¹²C, and ¹³C). Analysis of the experimental data and quantum-chemical calculations of vibrational spectra for the model compounds are used to identify the IR bands. New data are obtained on the vibrational spectra of these groups. Their identification is shown to be possible in the spectral range that is convenient for the study of silica samples.     

Low temperature absorption spectra of CrO 4 = in K2SO4 and VO 4 ≡ in Na3PO4 · 12H2O

The polarized absorption spectrum of the chromate ion has been measured at liquid hydrogen and helium temperatures. With chromate dissolved in K₂SO₄ evidence is found for two orbitally allowed ¹ A ₁¹ T ₂ electronic absorption bands. The first band is split into three sublevels with the 0-0 lines located at 26,316 cm^–1, 26,441 cm^–1 and 26,610 cm^–1. Built upon the 0-0 lines is seen a simple progression in quanta of 783 cm^–1. The second transition is nearly featureless, and is found at 34,000 cm^–1 to 44,000 cm^–1. The two bands are assigned as primarily t ₁2e and as 3t ₂2e respectively.VO ₄ dissolved in Na₃PO₄ · 12H₂O showed at liquid nitrogen temperature a broad featureless band found between 30,000 and 40,000 cm^–1.

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Zusammenfassung Das polarisierte Absorptionsspektrum des Chromations wurde bei den Temperaturen des flüssigen Wasserstoffs und Heliums gemessen. Für Chromat in K₂SO₄ werden zwei erlaubte Absorptionsbanden ¹ A ¹¹ T ₂ gefunden. Die erste Bande ist dreifach aufgespalten, ihre 0-0 Linien liegen bei 26316 cm^–1, 26441 cm^–1 und 26610 cm^–1. Von den 0-0 Linien ausgehend zeigt sich eine einfache Zunahme der Werte um 783 cm^–1. Der zweite Übergang ist nahezu strukturlos, er liegt zwischen 34000 cm^–1 und 44000 cm^–1. Die beiden Banden werden überwiegend t ₁2e bzw. 3t ₂2e zugeordnet. VO ₄ in Na₃PO₄ · 12H₂O zeigt bei der Temperatur des flüssigen Stickstoffs eine breite strukturlose Bande zwischen 30 000 und 40 000 cm^–1.

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Résumé Le spectre d'absorption en lumière polarisée de l'ion chromate a été mesuré aux températures de l'hydrogène et de l'hélium liquide. Pour le chromate dissous dans K₂SO₄ on met en évidence deux bandes d'absorption électronique de transition orbitale permise ¹ A ₁¹ T ₂. La première bande est séparée en trois sous niveaux dont les raies 0-0 se trouvent à 26,316 cm^–1, 26,441 cm^–1 et 26,610 cm^–1. A partir des raies 0-0 on distingue une période de 783 cm^–1. La seconde bande est presque non structurée et s'étend de 34,000 cm^–1 à 44,000 cm^–1. Les deux bandes sont décrites comme t ₁2e et 3t ₂2e respectivement.VO ₄ dissous dans Na₃PO₄ · 12H₂O révèle à la température de l'azote liquide une large bande sans structure entre 30,000 et 40,000 cm^–1.

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On leave of absence from Anorganisch Chemisch Laboratorium der Universiteit, Amsterdam.     

IR-Untersuchungen an B-Tris (dimethylamino) boroxin und B-Tris[dimethylamino (d6)] boroxin

Zusammenfassung In B-Tri(dimethylamino)boroxin zeigt — im Gegensatz zum B-Trimethoxyboroxin — die B–O-Hauptbande nur geringe Kopplung mit CH₃-Deformationsschwingungen. Die B–N-Valenzbande tritt hingegen mit _sCH₃ in Wechselwirkung, wodurch Banden mit gemischtem Schwingungscharakter entstehen. In der deuterierten Verbindung liegt BN verkoppelt mit BO bei 1461 cm^–1

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In B-Tri(dimethylamino)boroxin coupling between the B–O ring stretching main-band and CH₃ is weak in contrast to B-trimethoxyboroxine. Interference between BN and CH₃ leads to bands of mixed character, one of them is above 1500 cm^–1. In [(CD₃)₂NBO] BN coupled with BO is at 1461 cm^–1.

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Mit 2 Abbildungen     

IR spectra of diastereomeric (with respect to phosphorus) 2′, 3′-O-alkylphosphonates of nucleosides

In a study of the IR absorption spectra of diastereomeric (with respect to phosphorus) 2,3-O-alkylphosphonates of nucleosides it was shown that the IR spectra of the diastereomers differ at 820–860 (_O-P-O), 1040–1060 (_P-O-C), and 1250–1300 cm^–1 (_P=O). Higher _O=P and _P-O-C values and lower _O-P-O values are observed for the R isomers (as compared with the S isomers), and this provides a possibility for the determination of the orientation of the P=O group relative to the protons of the phospholane ring in alkylphosphonates of nucleosides by comparison of the spectra of the diastereomers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 181–184, February, 1979.     

Endo and Exo Coordination to Cofacial Binuclear Copper(II) Complexes

A structural study of internal (endo) and external (exo) coordination to cofacial binuclear complexes is reported.Cu₂(NBA)₂(NBAH₂=3,3'-[2,7-naphthalenediylbis(methylene)]-bis(2,4-pentanedione)) is large enough to accommodate 2-methylpyrazine as an intramolecularly coordinated guest molecule Cu₂(NBA)₂((2Mepyz))4CH₂Cl₂Cu₂C₅₃H₅₈N₂O₈Cl₈, orthorhombic, space group Pnma (No. 62); a = 22.4674(11); b = 22.230(2); c = 11.4520(6) Å V = 5719.6(6) ų (at 100 K); Z = 4; R = 0.058; R _w = 0.167 for 344 parameters and 5339 reflections with I > 2(I). The Cu₂(NBA)₂(-(2-Mepyz)) molecules possess crystallographic m symmetry, with the CuCu vector (CuCu' 7.4801(8) Å) perpendicular to the mirror plane; this requires disorder in the 2-Mepyz guests. The two ``Cu(acac)₂' moieties (acacH = 2,4-pentanedione) are not quite parallel (dihedral angle between (acac)₂ planes = 3.93(7)^circ), forming a slightly wider opening on the side of the methyl group in the 2-Mepyz guest. On the other hand, the cavity in Cu₂(XBA)₂ (XBAH₂ = 3,3'-[1,3-phenylenebis(methylene)]-bis(2,4-pentanedione)) is smaller, so that CH₃CN must bind externally.Cu₂(XBA)₂(CH₃CN)₂1.5CH₃CNH₂O,Cu₂C₄₃H_52.5N_3.5O₉, monoclinic, space group P2₁/c (No. 14); a = 11.7361(16); b = 14.197(3); c = 13.299(3) Å; = 92.22(2)^{^}; V = 2214.3(7) ų (at 100 K); Z = 2; R = 0.044; R _w = 0.124 for 275 parameters and 4983 reflections with I > 2 (I). This structure contains centrosymmetric Cu₂(XBA)₂ units (CuCu' 4.8302(12) Å) with externally coordinated CH₃CN ligands. The crystal packing in Cu₂(NBA)₂((2Mepyz))4CH₂Cl₂,which contains close contacts between layers of Cu₂(NBA)₂(-(2-Mepyz)) moieties, is also similar to that in three other crystalline host–guest adducts M₂(NBA)₂(-G). Cu₂(XBA)₂(CH₃CN)₂1.5CH₃-CNH₂O does not contain similar layers of molecules, presumably because the adduct molecules do not have the same type of exposed flat surfaces.     

The viscoelasticity of spinnable solutions of alkyltrimethylammonium salicylates

The viscoelasticity has been measured for aqueous solutions of tetradecyl-and hexadecyltrimethylammonium salicylates (C₁₄TASal, C₁₆TASal). The aqueous solutions of C₁₄TASal without salt displayed the gel-like behavior at 10.0×10^–2 g cm^–3, but those more dilute than 3.2×10^–2 g cm^–3 presented the viscoelasticity similar to that of a Maxwell liquid. The Maxwell-like behavior was converted to the polymer-like one on the addition of (0.1–0.2) M NaBr or (0.02–0.2) M NaSal. The gel-like viscoelasticity can be connected with the spinnability of cohesive fracture failure, and the Maxwell-like and polymer-like viscoelasticities are concerned with the spinnability of ductile failure. The gel-like and Maxwell-like viscoelasticities originate in the pseudo-network formed by the pseudo-linkages between rodlike micelles, while the polymer-like viscoelasticity is caused by the entanglement of long rodlike micelles in semidilute and concentrated solutions. The aqueous solutions of C₁₆TASal behaved very similar to those of C₁₄TASal.     

Crystal Structures of Two New Holmium Polysulfides in the Series of Rare-Earth Polychalcogenides

The crystal structures of two polysulfide phases HoS_1.885(5) (I) and HoS_1.863(8) (II) were determined; the integer stoichiometric ratio was found to be Ho₈S₁₅. The data were collected on an Enraf-Nonius CAD-4 automatic diffractometer using the standard procedure (MoK, graphite monochromator, an absorption correction applied based on -scan data). Crystal I: space group P4/nmm, a = 3.820(1), c = 7.840(3) , V = 114.40(6) ³, Z = 2 for the composition HoS_1.885(5), d _calc = 6.542 g/cm³, R = 0.0520 for 184 unique reflections with I_hkl > 2 _I; crystal II: space group P2₁/m, a = 10.961(2), b = 11.465(2), c = 10.984(2) , = 91.27(3)°, V = 1380.0(4) ³, Z = 24 for the composition HoS_1.863(8), d _calc = 6.486 g/cm³, R = 0.0596 for 5354 unique reflections with I_hkl > 2 _I. In both compounds, the Ho atoms are surrounded by 9 (8+1 for three atoms in II) S atoms forming monocapped square antiprisms. The Ho–S distances vary from 2.717 to 3.067 irrespective of the type of ion [S^2– or (S₂)^2–]; the maximal distance to the atoms completing the coordination is 3.684 . The compounds have PbFCl type structures composed of ...(S₂)^2–...Ho³⁺...S^2–...S^2–...Ho³⁺...(S₂)^2–... layer packets differently oriented in space relative to the unit cell axes. The S^2–...S^2– and S^2–...(S₂)^2– interlayer distances are mostly shorter than the sum of the ionic radii and vary within the limits of 3.331-3.558 and 3.029-3.784 for the first and second types, respectively. For I, the calculated site occupancies and densities are given depending on the composition Ho-S_2-x (x = 0.25-0); for II, the most probable formulas of rational compositions in the same range of x are presented.     

Force constant calculations of the LAM-1 modes ofn-alkanes and their substituted α-Monohalo- and α,ω-dihalo- species in their extended zig-zag planar configurations as found in urea inclusion compounds

Force constants were determined for the C₈, C₁₀, C₁₂ and C₁₄ series ofn-alkanes C _n H_{2n + 2} using an approximate SVFF calculation and observed LAM = 1 wave numbers. In this calculation the hydrogen atoms were neglected and only the carbon backbone chain and terminal atoms were considered; this was valid since only low-frequency vibrations were under consideration. Using force constant transfer, the wavenumbers of the LAM = 1 accordion modes for the analogous -C_n H_2n + 1 X and ,-C_n H_2nX₂ species, where X = C1, Br or I were calculated. For -chloroalkanes and ,-dichloroalkanes, them = 1 accordion modes are calculated to be in the 220–130 cm^–1 and 200–120 cm^–1 regions, respectively. For the bromo- and iodo-analogues them = 1 accordion modes are calculated to be in the 200–100 cm^–1, 150–90 cm^–1 and in the 170–100, 135–80 cm^–1 regions, respectively.     

Pressure effects on aminonaphthalene dye fluorescence in H2O and D2O

The pressure dependence of excited-state proton transfer equilibria has been examined for aqueous solutions of several substituted napthalene dyes, in particular 1-dimethylaminonaphthalene-5-sulfonic acid (DANS). The pressure-induced shift in equilibrium is characterized by volume changes spanning the range V ^*=–18 cm³ mole^–1 to V ^*=+4 cm³-mole^–1. A deuterium oxide solvent isotope effect is evident in the pressure response of DANS, leading to a 35% smaller V_* in D₂O relative to H₂O.     

Atranes

The infrared absorption spectra over the range 400–1700 cm^–1 of ten organyl- and organoxysilatranes, p-CH₃C₆H₄O] are investigated. The SiN coordinate link in these compounds is largely unreflected in the fundamental vibration frequencies of the bonds of the central silicon atom or the internal vibration frequencies of the substituents X linked to that atom. However, all the IR spectra have an absorption band in the 570 cm^–1 region, related to the valence vibrations (SiN), or manifesting itself as the frequency (Si-O) of the XSi (O)₃ group, substantially lowered because of interaction between the Si-O and Si-N bonds. Evidence in favor of this bond is shift of the (Si-H) frequency in the spectrum of silatrane(X=H).For Part V see [1].     

Study of a hollow cathode arc discharge in the presence of chromium oxide

A hollow cathode arc discharge in hydrogen has been used for the purpose of chromium oxide reduction, the solid oxide being placed inside the anode. Mass transport from the oxide to the gas phase and excitation conditions in the plasma have been investigated. The results show that a substantial amount of oxide is transferred to the gas phase with subsequent reduction and deposition inside the cathode cavity, in the form of a pure metal. The residual part condenses on the discharge chamber wall as an amorphous substance, containing 50–60% of Cr metal, and on the anode surface under the form of a mixture of chromium oxide and metal crystals (10%). From spectroscopic investigations it follows that, inside the anode zone, total Cr concentration in the gas phase is of the order of 10¹⁴ cm^–3, the excitation temperature of the atoms and ions being 4500 and 5500 K, respectively, and the ionization temperature being about 6000 K.Notation I absolute spectral line intensity (W cm^–2 sr^–1) - emission coefficient (W cm^–3 sr^–1) - A relative absorption - absorption coefficient (cm^–1) - L plasma diameter (mm) - f _tk oscillator strength - _D full Doppler width (cm^–1) - S( ₀ L) Ladenburg-Levy function - wave number (cm^–1) - k _pl mass transport rate (mol cm^–2 s^–1) - k _th thermal reduction rate (mol cm^–2 s^–1) - u ion mobility (mm V^–1 s^–1 ) - E electric field strength (V mm^–1) - drift velocity (cm s^–1)     

Superionic conductivity in (BEDT-TTF)AgXiY

We have synthesized the organic conductor (BEDT-TTF)Ag_XI_Y (X 1.8 and Y 2.9). This compound has, in addition to high electronic conductivity (_{300 k} 5–10 ^–1 · cm^–1), significant ionic conductivity connected with the motion of silver ions. The value of this ionic conductivity at room temperature is 10^{–3 –1} · cm^–1. The activation energy for diffusion of Ag ions is equal to 0.2 eV.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 247–249, March–April, 1989.     

Die Schwingungsspektren von Trimethylsilyl-alkyl-bzw.-phenyl-aminen

Zusammenfassung Die Infrarot- und die Raman-Spektren der Silylamine (CH₃)₃Si–NH–R (R=CH₃, C₂H₅ und C₆H₅) sowie der analogen N-deuterierten Verbindungen werden mitgeteilt und analysiert. Starke Kopplungen führen zu einer Mischung vonv SiN bei etwa 700 cm^–1 mit anderen Schwingungen des C₃Si–NHR-Skelettes.

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The Infrared and Raman spectra of the silylamino compounds (CH₃)₃Si–NH–R (R=CH₃, C₂H₅, and C₆H₅) and the analogous N-deuterated species are reported and assigned. The SiN stretching mode at about 700 cm^–1 is strongly coupled with other vibrations of the molecules.