Fourier-transform infrared spectrum of aspartate hydroxo-aqua nickel (II) complex and DFT-B3LYP/3-21G and 6-311G structural and vibrational calculations

Aspartate hydroxo-aqua nickel (II) complex was synthesized and the structural analysis was carried out through the following methods: determination of the C, N, O and H contents, thermogravimetry and infrared spectrum. Several hypothetic structures were calculated by means of DFT: B3LYP/3-21G and B3LYP/6-311G quantum mechanical method. For [Ni(Asp)(OH)(H(2)O)] we have obtained the minimum of energy and no imaginary frequencies in the calculated infrared spectrum. Moreover, the experimental FT-infrared spectrum shows that the two N-H stretching follow the Bellamy-Williams relation proposed for primary amines. Coordination water bands were also observed in the infrared spectrum. For reasons of accomplishment, the Fourier transforms infrared and Raman spectra of acid aspartic were also discussed.     

Multiplex coherent anti-Stokes Raman microspectroscopy with tailored Stokes spectrum

We combined the ultrabroadband supercontinuum of a photonic crystal fiber with a pulse shaper, resulting in a highly flexible light source for multiplex coherent anti-Stokes Raman microscopy. Implemented as the Stokes pulse, it provides tailored selection of the relevant Raman transitions, resulting in a reduced photon load and partial suppression of the nonresonant background. This experiment exploits the advantages of multiplex excitation with the increased acquisition speed of single-channel detection. The molecule-specific Stokes pulses are demonstrated for chemical mapping of a polymer blend.     

A large deviations principle for stochastic flows of viscous fluids

We study the well-posedness of a stochastic differential equation on the two dimensional torus ${\mathbb{T}}^2$, driven by an infinite dimensional Wiener process with drift in the Sobolev space $L^2(0,T;H^1\left({\mathbb{T}}^2\right))$. The solution corresponds to a stochastic Lagrangian flow in the sense of DiPerna Lions. By taking into account that the motion of a viscous incompressible fluid on the torus can be described through a suitable stochastic differential equation of the previous type, we study the inviscid limit. By establishing a large deviations principle, we show that, as the viscosity goes to zero, the Lagrangian stochastic Navier–Stokes flow approaches the Euler deterministic Lagrangian flow with an exponential rate function.     

Deformation and rigidity results for the 2k‐Ricci tensor and the 2k‐Gauss‐Bonnet curvature

We present several deformation and rigidity results within the classes of closed Riemannian manifolds which either are 2k‐Einstein (in the sense that their 2k‐Ricci tensor is constant) or have constant 2k‐Gauss‐Bonnet curvature. The results hold for a family of manifolds containing all non‐flat space forms and the main ingredients in the proofs are explicit formulae for the linearizations of the above invariants obtained by means of the formalism of double forms.     

On some polynomials enumerating Fully Packed Loop configurations: Evaluation at negative values

In this article, we are interested in the enumeration of Fully Packed Loop configurations on a grid with a given noncrossing matching. These quantities also appear as the groundstate components of the O(n)$O(n)$ Loop model as conjectured by Razumov and Stroganov and recently proved by Cantini and Sportiello.     

Quantum control spectroscopy of vibrational modes: Comparison of control scenarios for ground and excited states in β-carotene

Quantum control spectroscopy (QCS) is used as a tool to study, address selectively and enhance vibrational wavepacket motion in large solvated molecules. By contrasting the application of Fourier-limited and phase-modulated excitation on different electronic states, the interplay between the controllability of vibrational coherence and electronic resonance is revealed. We contrast control on electronic ground and excited state by introducing an additional pump beam prior to a DFWM-sequence (Pump-DFWM). Via phase modulation of this initial pump pulse, coherent control is extended to structural evolution on the vibrationally hot ground state (hot-S₀) and lowest lying excited state (S₁) of β-carotene. In an open loop setup, the control scenarios for these different electronic states are compared in their effectiveness and mechanism.     

Use of microdevices to determine the diffusion coefficient of electrochemically generated species: application to binary solvent mixtures and micellar solutions

A new approach for the determination of diffusion coefficient, D, of redox species is presented. It is based on the use of a home-constructed twin electrode within a thin-layered cell (TETLC) filled with a solution of electroactive species. Values of D are readily calculated, provided that the time required for the electrochemically generated species (produced at the generator electrode) to reach the collector electrode and the distance between both electrodes are known. Other parameters typically required to calculate D, e.g., concentration of the redox species, area of the electrode, and number of electrons transferred, are not needed. Diffusion coefficients of Fe(CN)(6)(3-), Ru(NH3)(6)(2+), and quinone were determined in water and, for Fe(CN)(6)(4-), in binary mixtures with glycerol. The results obtained were in good agreement with literature values. Aqueous glycerol solutions are microheterogeneous, as shown by the dependence on medium composition of the empirical solvent polarity scale, ET(30), determined by the solvatochromic probe RB. The responses of RB and the electrochemically generated species (Fe(CN)(6)(4-)) to the composition of aqueous glycerol mixtures were found to be remarkably similar. Measurements of D of ferrocene in micellar solutions of the cationic surfactant CTABr were also performed. Values of D for ferrocene and the ferrocenium cation are very different, in agreement with the chemical affinity of both species for the cationic micelle.     

Enhancement of molecular modes by electronically resonant multipulse excitation: further progress towards mode selective chemistry

We show that molecular vibrations induced by resonant excitation pulses can be enhanced by pulse trains, compared to Fourier-limited pulses of equal pulse energy. As a proof-of-principle, a low frequency mode of Nile Blue at 600 cm(-1) is observed and amplified in a pump and probe experiment. In addition to previous experiments in our group, an increased population transfer to the excited electronic state is identified as an important element of the underlying physical mechanism. These results suggest an enhancement on the level of individual molecules rather than a macroscopic effect.