High-resolution analysis of the ν1 and ν5 bands of phosgene 35Cl2CO and 35Cl37ClCO

Fourier transform spectra of phosgene (Cl₂CO) have been recorded in the 11.75 and 5.47 μm spectral regions using a Bruker IFS125HR spectrometer at resolutions of 0.00102 and 0.0015 cm^?1, respectively, leading to the observation of the ν₅ and ν₁ vibrational bands of the two isotopologues ³⁵Cl₂CO and ³⁵Cl³⁷ClCO. The corresponding upper state ro-vibrational levels were fit using Watson-type Hamiltonians and/or a Hamiltonian matrix accounting for resonance effects when necessary. In this way, it was possible to reproduce the upper state ro-vibrational levels to within the experimental accuracy, i.e. ～0.17 × 10^?3 cm^?1. Very accurate rotational and centrifugal distortion constants were derived from the fit together with the following band centres: ν₀(ν_5, ³⁵Cl₂CO) = 851.012737(20) cm^?1, ν₀(ν_5, ³⁵Cl³⁷ClCO) = 849.995451(90) cm^?1, ν₀(ν_{2 +} ν_3, ³⁵Cl³⁷ClCO) = 864.42370(50) cm^?1, ν₀(ν_1, ³⁵Cl₂CO) = 1828.202514(40) cm^?1 and ν₀(ν_1, ³⁵Cl³⁷ClCO) = 1827.246444(20) cm^?1.     

The role of basic amino acids in the molecular recognition of hydroxyapatite by statherin using solid state NMR

Organisms use proteins such as statherin to control the growth of hydroxyapatite (HAP), which is the principal component of teeth and bones. Though much emphasis has been placed on the acidic character of these proteins, the role of their basic amino acids is not well understood. In this work, solid state nuclear magnetic resonance was used to probe the interaction of the basic arginine side chains with the HAP surface. Statherin samples were individually labeled at each arginine site, and the distance to the surface was measured using the Rotational Echo DOuble Resonance (REDOR) technique. The results indicate a strong coupling between the R9 and R10 residues and the phosphorus atoms on the surface, with internuclear distances of 4.62 ± 0.29 Å and 4.53 ± 0.16 Å, respectively. Conversely, results also indicate weak coupling between R13 and the surface, suggesting this residue is more removed from the surface than R9 and R10. Combining these results with previous data, a new model for the molecular recognition of HAP by statherin is constructed.     

First far-infrared high-resolution analysis of the ν2 and ν4 bands of phosgene 35Cl2CO and 35Cl37ClCO

ABSTRACT

A Fourier transform spectrum of phosgene (Cl₂CO) has been recorded in the 17.3-μm spectral region at a temperature of 180 K and at a resolution of 0.00102 cm^?1 using a Bruker IFS125HR spectrometer coupled to synchrotron radiation, leading to the observation of the ν₂ and ν₄ vibrational bands of the two isotopologues ³⁵Cl₂CO and ³⁵Cl³⁷ClCO. The corresponding upper-state ro-vibrational levels were fit using a Hamiltonian model accounting for the A-type Coriolis interaction linking the rotational levels of the 2¹ and 4¹ vibrational states. In this way, it was possible to reproduce the upper-state ro-vibrational levels to within the experimental uncertainty, i.e. ～0.30 × 10^?3 cm^?1. Very accurate rotational and centrifugal distortion and interaction constants were derived from the fit, together with the following band centres: ν₀(ν_2, ³⁵Cl₂CO) = 572.526299(30) cm^?1, ν₀(ν_4, ³⁵Cl₂CO) = 582.089026(30) cm^?1, ν₀(ν_2, ³⁵Cl³⁷ClCO) = 568.951791(35) cm^?1 and ν₀(ν₄, ³⁵Cl³⁷ClCO) = 581.758279(35) cm^?1.     

Screening constant by unit nuclear charge calculations for (n s2)1Se, (np2)1De and (N s n p)1P○ excited states of He-like systems

Screening Constant by Unit Nuclear Charge (SCUNC) is a new analytical method suitable for the treatment of the properties of He-like systems. In this paper, the possibilities of the method are demonstrated for calculating in the framework of semi-empirical procedure, total energies, total electron-electron interaction energies and excitation energies for (ns²)¹S^e, (np²)¹D^e and (Nsnp)¹P° doubly excited states of He-like ions. The proposed semi-empirical scheme, leads to accurate results in good agreement as well as with available other theoretical results than experimental data.     

Polarization sensitive sub-wavelength metallic structures: toward near-field light confinement control

In this paper, we seek to demonstrate spatial near field light confinement with a truly sub-wavelength resolution in the visible range. For that purpose, an opaque metallic screen is pierced with an array of rectangular nano-apertures which support polarization sensitive guided modes. We show that it is possible to switch on and off sub-wavelength apertures about only 200 nanometers away. Theoretical results have been performed (3D-FDTD home-made code) and are in good agreement with the experimental results. These kinds of nano-structures might offer a convenient and versatile way to sub-wavelength light addressing, optical trapping, molecular, or nano-probing, non-linear spectroscopy.     

Sensitized Luminescence of Trivalent Lanthanide Complexes Eu3+/Quinaldinic Acid and Eu3+/1,4-Dihydro-Oxo-Chinoline-3-Carboxilic Acid

Studies of the luminescence of Eu(3+)/quinaldinic acid sodium [Eu(QA)(3)] and Eu(3+)/1,4-dihydro-4-oxo-quinoline-carboxylic acid sodium [Eu/(DOQCA)(3)], both in solid form and in aqueous solution, are presented in room temperature. The energy transfer to the emitting levels of the lanthanide ions are discussed on the basis of the emission spectra and lifetime data of (5)D(0) and (5)D(1) levels of Eu(3+). In the aquated Eu/(QA)(3) complex, the most intense spectral band belongs to the (5)D(0) --> (7)F(1) transition (592 nm) and not to (5)D(0) --> (7)F(2) (616 nm), which otherwise occurs usually. In the cases of the Eu/(DOQCA)(3) complex the hypersensitive transition (5)D(0) --> (7)F(2) is the most intense as so far was reported for various Eu(3+) chelates.