Vibrational dynamics of ions in glass from fifth-order two-dimensional infrared spectroscopy

The vibrational dynamics of the first four antisymmetric stretch vibrational levels of azide in an ionic glass have been measured and correlated using a heterodyned fifth-order two-dimensional infrared pulse sequence. By rephasing a two-quantum coherence, a process not possible with third-order spectroscopy, solvent effects on the frequencies and anharmonicities of the potential energy surface are measured. Fifth-order pulse sequences are another step towards precisely controlling vibrational coherence in analogy to the manipulation of spins in NMR but with ultrafast time resolution.     

Photochemical fragmentation of mesotonic 1,3,4-thiadiazoles: a mechanistic observation

Photochemistry, synthesis, nucleophilic addition photoreaction, low temperature photolysis, and quantum yield calculations of representative members have been studied in understanding the mechanism of the photofragmentation of mesoionic 1,3,4-thiadiazoles. Quantum yield calculations suggest self quenching and unimolecularity in the ring opening reaction while timed interval IR recording shows the formation of heterocumulenes during photolysis.     

Study of single phase YBa2Cu3O7−δ compound around 1–2–3 stoichiometry

The structural changes accompanying small stoichiometric variations around 1–2–3 composition in the Y-Ba-Cu-O compound have been investigated. Ba-deficient composition is found to give considerable orientation along (001). This oriented powder gives a higher current density compared to the unoriented powder. The temperature has been correlated with stoichiometry.     

Paper chromatographie studies on periodic precipitation

Summary An investigation of the nature of the rhythmic patterns obtained by diffusing the reactant solution on the circular filter papers impregnated with precipitating agents and a protective colloid (2% agar agar) has been made. The systems: AgNO₃–K₂CrO₄, Pb(NO₃)₂–K₂CrO₄, Ba(NO₃)₂–K₂CrO₄, Co(NO₃)₂–K₄Fe(CN)₆, and Co(NO₃)₂–K₃Fe(CN)₆ have been studied. An attempt has been made to explain the radial and ring rhythmicity on filter papers on the basis of coagulation theory ofDhar andChatterji.     

Gel-derived single layer antireflection films

A process based on the sol-gel process has been developed to deposit single layer alkaliborosilicate antireflection films on glass substrates for high power laser use. A partially polymerized solution in the Na₂OB₂O₃SiO₂ system prepared by the sol-gel process was deposited by the dipping technique. The gel-derived films after thermal treatment below 500°C were leached with acid leachants to leach the leachable phase and to change the pore morphology in a controlled way so that a refraction index gradient develops. The reflectivities of the heat treated leached films were in the range 0.15–0.7% at 1.06 μm wavelength. Laser damage thresholds of these films are four times greater than those of multilayer antireflection films.     

Production possibility of <Superscript>61</Superscript>Cu using proton induced nuclear reactions on zinc for PET studies

Summary Excitation functions were measured by stacked-foil technique for the ^natZn(p,x)⁶¹Cu, ⁶⁶Zn(p,x)⁶¹Cu, ⁶⁸Zn(p,x)⁶¹Cu and ^natZn(p,x)⁶⁰Cu nuclear processes up to 100 MeV. The experimental cross sections were compared with published data. On the base of these excitation functions, the cross sections of ⁶⁴Zn(p,x)⁶¹Cu process were also deduced. Integral thick target yields were calculated for the ⁶⁴Zn(p,x)⁶¹Cu and ^nat,64Zn(p,x)⁶⁰Cu processes and irradiation parameters were elaborated for the ⁶¹Cu production via the ⁶⁴Zn+p reactions for low and middle energy accelerators. According to our calculations the yield of ⁶¹Cu amounts to 1.02 ^. 10¹¹ Bq ^. A^{-1 .} s^-1 (9.9 mCi ^.µ A^{-1 .} h^-1) from 19®10 MeV while it reaches 3.91 ^. 10¹¹ Bq ^. A^{-1 .} s^-1 (38 mCi ^{. µ} A^{-1 .} h^-1) in the energy range of 67®60 MeV.     

Synthesis of oxepine-, oxocine- and azepine-annulated carbazole derivatives by combined Claisen rearrangement and diene/enyne metathesis

A new route to various medium ring heterocycle-annulated tetra-, penta- and hexacyclic carbazole derivatives has been developed using successive applications of three atom economic processes, viz. Claisen rearrangement, olefin metathesis and Diels-Alder reactions.     

Synthesis and X‐ray structure of two conformational isomers of [Zn(medpt)(SCN)2], medpt = bis (3 – aminopropyl)methylamine

Two conformational isomers of [Zn (medpt)(NCS)₂], medpt=bis(3‐aminopropyl) methylamine, (1) and (2) have been synthesised and the crystal structures are determined using single crystal X‐ray diffraction. The structures of the complexes have been solved by Patterson method and refined by full‐matrix least‐ squares techniques to R1 = 0.0524 for (1) and R1 = 0.0506 for (2), respectively. The geometry around the Zn(II) centre in both isomers is distorted trigonal bipyramidal. The two pendent thiocyanate moieties in (1), with Zn–N–C angles 167.9(4)–173.9(4)º, coordinate the mental centre almost linearly while the corresponding coordinations in (2) are significantly bent [Zn–N–C angles 150.8(3)–153.1(2)°]. Intermolecular N–H…S hydrogen bonds stabilise the crystal packing in the complexes forming infinite chains parallel to the [100] direction. The combinations of molecular chains generate three/two dimensional supramolecular framework in complexes (1) and (2). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)