Lateral growth rates in laser CVD of microstructures

Lateral growth rates of Ni spots deposited on absorbing substrates by decomposition of Ni(CO)₄ with visible Kr⁺ laser light have been measured. The experimental data are consistent with the calculated temperature distributions. The mechanism of decomposition is thermal with an apparent chemical activation energy of 22±3 kcal/mole for the temperature range 350 KT500 K.     

Synthesis of benzofuro[3,2-b] quinolin-6(11H) one and derivatives

A new and efficient synthesis of benzof'uro[3,2-b]quinolin-6(11H) one ( 3 ) is reported, by treatment of 2- {[(phenoxy)acetyl]amino} benzoic acid ( 6a ) with polyphosphoric acid. An intermediate in the conversion of 3 to 6a , namely, 2-(3-benzofuranylamino)benzoic acid ( 7 ), was defined. An improved method for the synthesis of 6a is also described, which was used to prepare analogs ( 6b-n ) of 6a . In addition, an 11-alkoxy derivative ( 8 ) and 11-dialkylamino derivatives ( 10 and 11 ) of benzofuro [3,2-b]quinoline were prepared from 3 .     

Synthesis of [(MeCyt)2H]I-structure and stability of a dimeric threefold hydrogen-bonded 1-methylcytosinium 1-methylcytosine cation

Reaction of trimethylsilyl-protected cytosine with methyl iodide afforded N1-methylated product. Subsequent treatment with ethanol resulted in cleavage of the protection group forming [(MeCyt)2H]I (4). Identity of was confirmed by microanalysis, mass spectrometry, 1H and 13C NMR spectroscopy and by single-crystal X-ray diffraction analysis. Crystals of consist of dimeric [(MeCyt)2H]+ cations and I- anions. These ions are arranged in the crystal such that there is a strong base stacking (mean stacking distance 3,467 angstroms) and, furthermore, pi interactions between I- and cytosine rings (mean distance 3,737 angstroms). The dimeric [(MeCyt)2H]+ cations are centrosymmetric having three strong hydrogen bonds, namely two terminal N4-H...O' ones (N4...O' 2.815(4) angstroms) and a central N3-H...N3' (N3...N3' 2.813(4) angstroms) one. Quantum chemical calculations on the DFT level of theory show that the gas phase structure of the dimeric cation exhibits two different terminal N-HO hydrogen bonds, a stronger (N4...O' 2.722 angstroms) and a weaker one (N4'...O 2.960 angstroms). The central N3-HN3[prime or minute] hydrogen bond (N3...N3' 2.852 angstroms) was characterized to have an unsymmetrically located proton and a typical double minimum potential with a very low activation barrier. The interaction energy between [(MeCyt)H]+ and MeCyt yielding [(MeCyt)2H]+ was calculated to be -42.4 kcal mol(-1)(ZPE and BSSE corrected). Comparison with the interaction energy (calculated on the same level of the theory) between cytosine and guanine yielding the triply hydrogen-bonded Watson-Crick dimer (-24.2 kcal mol(-1)) revealed a much higher stability of the hydrogen bonds in [(MeCyt)2H]+.     

A coupled electron diffraction and rigid unit mode (RUM) study of the crystal chemistry of some zeotypic AlPO4 compounds

Electron diffraction and lattice dynamical calculations are used to investigate the unit cells, space group symmetries and inherent displacive flexibility of the room-temperature average structures of AlPO₄-8, AlPO₄-16 and AlPO₄-tridymite. The zero-frequency rigid unit modes (RUMs) of the idealized high-symmetry polymorphs thereof are also investigated along with their relationship to the lower-temperature polymorphism of these zeotypic aluminophosphates. The clear presence of satellite reflections in addition to the Bragg reflections (G) of the underlying Cmc2₁ parent structure in the case of AlPO₄-8 shows that the true unit cell of the room-temperature polymorph has a doubled c-axis due to a condensed RUM mode. Structured diffuse scattering is also observed which can be related to the thermal excitation of RUM modes. In the case of AlPO₄-tridymite, a complex F1 triclinic polymorph is observed and related to soft RUM modes while, in the case of AlPO₄-16, a soft q=0 RUM mode is shown to be responsible for an observed phase transition in the case of the all SiO₂ analogue of AlPO₄-16. A large number of additional zero-frequency RUM modes also exist in the case of AlPO₄-16.     

Iodine photodissociation laser system Perun II

A construction and exploitation of a medium size iodine photodissociation laser system Perun II is reported. This laser produced pulses of infrared light (=1.315m) up to 50 J in energy and 300 ps in duration. The diameter of the beam is 82 mm. The beam divergence is about 4×10^–4 rad. The laser beam can be focused in a focal spot of a power density exceeding 10¹⁴ W/cm². The resuls of measurements of basic plasma parameters on an Al foil target are also presented. A recent improvement of the system includes a conversion to the second harmonic by a DKDP crystal.Presented at bilateral international seminar of High Temperature Laser Plasma and High Gain Iodine Lasers held on 4 July 1991 in the Inst. of Physics, Czechosl. Acad. Sci., in Prague (organized by Division of Optics of the Inst. of Physics, Czechosl. Acad. Sci., and Physical Section (Plasma Division) of the Union of Czech Mathematicians and Physicists.     

Non-isothermal studies of adduct molecules of metallic halides with oxo-compounds in solid state. V

Non-isothermal studies of some adduct molecules of metallic halides with tetrahydropyran as the type MX₂(THP)_y in solid state, were carried out with a Derivatograph, where M  Mn(II), Co(II), Ni(II), Cu(II) or Cd(II), XCl^- or Br^-, THPtetrahydropyran and y0.1–1. These adduct molecules lost tetrahydropyran in single or multiple steps upon heating. Thermally stable intermediate products were isolated and characterised by elemental analysis and IR spectral measurement. The activation energy for each step of decomposition of the adduct was evaluated from the analysis of TG, DTG and DTA curves of the respective derivatogram. The enthalpy change was evaluated from the DTA peak area and the order of reaction was found to be unity, for each step of decomposition. Thermal parameters for the above adducts were compared with the adducts of other oxocompounds like dioxan, tetrahydrofuran, ethylene glycol dimethyl ether and diisopropyl ether.     

A note on debye potentials for spherically gyrotropic media

The Debye potentials are generalized to the case of electromagnetic fields in spherically gyrotropic media. A medium is called spherically gyrotropic if it is locally gyrotropic with the distinguished axis having a radial direction determined by a central point. Expressions for electromagnetic fields in terms of the generalized potentials are presented and the system of differential equations for the potentials is derived. The results are summarized in the form of a theorem. Basic facts about the Debye potentials in isotropic media are recalled.     

Some remarks on the approximation in the strong sense

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On the 70th birthday of Professor S. M. Nikol'skii