Infrared identification of matrix isolated H2O.O2

Theoretical studies of the H2O.O2 complex have been carried out over the past decade, but the complex has not previously been experimentally identified. We have assigned IR vibrations from an H2O.O2 complex in an inert rare gas matrix. This identification is based upon theoretical calculations and concentration dependent behavior of absorption bands observed upon co-deposition of H2O and O2 in argon matrixes at 11.5 +/- 0.5 K. To aid assignment, we have used a harmonically coupled anharmonic oscillator local mode model with an ab initio calculated dipole moment function to calculate the OH-stretching and HOH-bending frequencies and intensities in the complex. The high abundance of H2O and O2 makes the H2O.O2 complex likely to be significant in atmospheric and astrophysical chemistry.     

2-Tangles

Just as links may be algebraically described as certain morphisms in the category of tangles, compact surfaces smoothly embedded in R⁴ may be described as certain 2-morphisms in the 2-category of 2-tangles in four dimensions. In this announcement we give a purely algebraic characterization of the 2-category of unframed unoriented 2-tangles in four dimensions as the free semistrict braided monoidal 2-category with duals on one unframed self-dual object. A forthcoming paper will contain a proof of this result using the movie moves of Carter, Rieger and Saito. We comment on how one might use this result to construct invariants of 2-tangles.     

Resonance Raman spectroscopy reveals new insight into the electronic structure of beta-hematin and malaria pigment

Resonance Raman spectra of beta-hematin and hemin are reported for a range of excitation wavelengths including 406, 488, 514, 568, 633, 780, 830, and 1064 nm. Dramatic enhancement of A(1g) modes (1570, 1371, 795, 677, and 344 cm(-1)), ring breathing modes (850-650 cm(-1)), and out-of-plane modes including iron-ligand modes (400-200 cm(-1)) were observed when irradiating with 780- and 830-nm laser excitation wavelengths for beta-hematin and to a lesser extent hemin. Absorbance spectra recorded during the transformation of hemin to beta-hematin showed a red-shift of the Soret and Q (0-1) bands, which has been interpreted as excitonic coupling resulting from porphyrin aggregation. A small broad electronic transition observed at 867 nm was assigned to a z-polarized charge-transfer transition d(xy) --> e(g)(pi). The extraordinary band enhancement observed when exciting with near-infrared excitation wavelengths in beta-hematin when compared to hemin is explained in terms of an aggregated enhanced Raman scattering hypothesis based on the intermolecular excitonic interactions between porphyrinic units. This study provides new insight into the electronic structure of beta-hematin and therefore hemozoin (malaria pigment). The results have important implications in the design and testing of new anti-malaria drugs that specifically interfere with hemozoin formation.     

Metalloporphyrin molecular sieves based on Tin(IV)porphyrin phenolates

[reaction: see text] The crystal and molecular structures of two six-coordinate tin(IV)porphyrin phenolate complexes show that infinite cylindrical channels of uniform pore dimension are formed along the crystallographic c-direction. The underlying recognition event responsible for the porosity is an extremely tight intermeshing of the meso-tolyl units between layers which is a result of Sn-O...H interactions. Thermogravimetric analysis and differential scanning calorimetry have been used to characterize the sieve-like materials.     

Manipulating biphotonic qutrits

Quantum information carriers with higher dimension than the canonical qubit offer significant advantages. However, manipulating such systems is extremely difficult. We show how measurement-induced nonlinearities can dramatically extend the range of possible transforms on biphotonic qutrits-three-level quantum systems formed by the polarization of two photons in the same spatiotemporal mode. We fully characterize the biphoton-photon entanglement that underpins our technique, thereby realizing the first instance of qubit-qutrit entanglement. We discuss an extension of our technique to generate qutrit-qutrit entanglement and to manipulate any bosonic encoding of quantum information.     

Discussion on a possible neutrino detector located in India

We have identified some important and worthwhile physics opportunities with a possible neutrino detector located in India. Particular emphasis is placed on the geographical advantage with a stress on the complimentary aspects with respect to other neutrino detectors already in operation.     

Interaction of atrazine with Laurentian humic acid

Ultrafiltration fractionation and liquid chromatography have been applied to study the binding and hydrolysis of polar herbicide atrazine on a stoichiometrically well characterized Laurentian humic acid. The main advantage of this method over gas chromatography is the simultaneous determination of both free and bound atrazine, hydroxyatrazine and copper(II) ion with satisfactory accuracy and precision. Atrazine binding requires extensive carboxylate site protonation but the binding sites represent only a very small fraction of total carboxylate of humic acid. The results show that binding of atrazine is not competitive with binding of the hydrolysis product hydroxyatrazine, the binding capacity is reduced at higher ionic strength or by cation competition for carboxylate and the atrazine binding constant and free energy of binding can be fitted by a single value at all pH values. The differences between atrazine binding by fulvic acid and humic acid can be ascribed to the structure difference, one being a flexible linear polymer and the other a three-dimensional colloidal gel particle.     

Emission of neutral molecules during UV laser ablation of a photolabile triazeno polymer

The neutral products of irradiating a photolabile triazeno-polymer with a pulsed laser at 248 nm (KrF excimer) were studied with time-of-flight (TOF) mass spectrometry. At fluences below 1.3 J/cm², N₂ is by far the most intense neutral product. Phenyl radical (mass 76) production was also observed. The leading edge of the N₂ TOF signal shows a shoulder corresponding to kinetic energies of about 1.1 eV, followed by a long tail that lasts hundreds of microseconds. The tail is attributed to delayed emission of reaction products from the polymer. The kinetic energy of the fast peak is attributed to direct ejection of products from surface sites undergoing exothermic decomposition. The fluence dependence of the N₂ signal is highly nonlinear and is shown to fit an Arrhenius equation.     

Efficient Photoinduced Electron Transfer in a Rigid U-Shaped Tetrad Bearing Terminal Porphyrin and Viologen Units

Apparently solvent-mediated and not through-bond photoinduced electron transfer (ET) takes place from the porphyrin (P) unit to the methylviologen (MV²⁺) unit in the rigid U-shaped molecules 1 (i.e., k_TS^ET>k_TB^ET; TS=through-solvent, TB=through-bond). The ratio of the rates of charge separation to charge recombination is greater than 1400:1.