Search results for "Polarizability"
showing 10 items of 240 documents
Anisotropic light-shift and magic-polarization of the intercombination line of Dysprosium atoms in a far-detuned dipole trap
2018
We characterize the anisotropic differential ac-Stark shift for the Dy $626$ nm intercombination transition, induced in a far-detuned $1070$ nm optical dipole trap, and observe the existence of a "magic polarization" for which the polarizabilities of the ground and excited states are equal. From our measurements we extract both the scalar and tensorial components of the dynamic dipole polarizability for the excited state, $\alpha_E^\text{s} = 188 (12)\,\alpha_\text{0}$ and $\alpha_E^\text{t} = 34 (12)\,\alpha_\text{0}$, respectively, where $\alpha_\text{0}$ is the atomic unit for the electric polarizability. We also provide a theoretical model allowing us to predict the excited state polari…
Novel azobenzene precursors for NLO active polyuretanes: Synthesis, quantum chemical and experimental characterization
2009
Abstract For the development of electro optical active polyurethanes six new derivatives of 2-{(2-hydroxyethyl)-[4-(4-nitrophenylazo)phenyl]amino}ethanol and two of 2-{(2-hydroxyethyl)-[4-(5-nitropyridin-2-ylazo)phenyl]amino}ethanol were synthesized by azocoupling reaction. Molecular geometry, hyperpolarizability βFF and ground state dipole moment μg were acquired by RHF ab initio (6–31G∗∗) calculations using HyperChem software package. To characterize NLO performance of synthesized azo compounds second order non linear coefficients d31 and d33 were measured as function of chromophore load in guest–host films (PMMA). Eight synthesized compounds can be grouped in four similar gross formula p…
Vers le contrôle de l'alignement et de l'orientation : théorie et expérience
2010
This thesis is about the control and characterisation of the alignment and orientation of molecules by ultra short laser pulses on a theoretical and experimental approach. Alignment corresponds to a symmetric angular distribution of the molecular axis peaked along the laser field axis, whereas orientation provides an asymmetric distribution favouring one spatial direction. Orientation by sudden two-colour (2+1) pulses is studied extensively for the non resonant case and conditions required for achieving significant orientation are explored. A second two-colour scheme, where the second harmonic is in quasi resonance with a vibrational level of the molecule, is also presented and discussed. T…
Dielectric polarization and polarizability of 1-pentanol+n-octane mixtures from static dielectric constant and refractive index data at 0,25 and 45�C
1990
Static dielectric constants and refractive indices of 1-pentanol+n-octane mixtures were measured in the temperature range between 0 and 45°C. Data discussed in terms of Kirkwood correlation factor and Lorentz-Lorenz molar refractivity give information on the short range intermolecular interactions between the components. The role played by the nonpolar n-octane in the destruction of 1-pentanol oligomers is also pointed out.
Considerations on the dipole moment of molecules forming the twisted intramolecular charge transfer state
1992
Several derivatives of dual-fluorescing dimethylaminobenzonitrile (DMABN) are compared regarding their ground and excited-state dipole moments extracted from electro-optical emission and solvatochromic measurements. The comparison includes bridged model compounds as well as compounds with different degrees of steric hindrance to planarity, as well as ester and carbazolyl derivatives. The results are discussed on the basis of the twisted intramolecular charge transfer (TICT) model, the most widely accepted model. They show that (i) the dipole moment of the A (TICT) state (long-wavelength band) shows only little solvent sensitivity (polarizability), (ii) this observed small dependence of the …
Getting discriminant functions of antibacterial activity from physicochemical and topological parameters.
2001
Linear discriminant analysis has been demonstrated to be a very useful tool in the selection and design of new drugs. Up to now we have used it through the search of a topological pattern of activity. In this work our goal is to calculate a complete set of physicochemical parameters using semiempirical (quantum chemical) calculations as well as topological indices (TIs) and try to find out any discriminant function for antibacterial activity through the combined use of both types of descriptors. The physicochemical parameters, such as heat of formation, HOMO, LUMO, dipole moment, polarizability, hyperpolarizability, PM3 generated IR vibrational frequencies, etc., were calculated using PM3 H…
Femtosecond polarization spectroscopy in molecular gas mixtures: Macroscopic interference and concentration measurements
2000
0021-9606; Raman-induced polarization spectroscopy (RIPS) experiments combined with homodyne detection have been conducted with a femtosecond laser at room temperature and low pressure (p < 2 atm) in CO2-N2 mixtures as well as in air (O2-N2 mixtures). Each molecule of the mixture produces its own time-dependent signal, measured as a series of recurring transients. Macroscopic interference is observed when transients of both molecules overlap in the time domain. This interference leads to a large modification of the signal, which is well reproduced by calculations. The total signal recorded in CO2-N2 or O2-N2 mixtures of known concentration is analyzed in order to measure the polarizability …
Molecular Dynamics Simulations of SFG Librational Modes Spectra of Water at the Water–Air Interface
2016
At the water–air interface, the hydrogen-bond network of water molecules is interrupted, and accordingly, the structure and dynamics of the interfacial water molecules are altered considerably compared with the bulk. Such interfacial water molecules have been studied by surface-specific vibrational sum-frequency generation (SFG) spectroscopy probing high-frequency O–H stretch and H–O–H bending modes. In contrast, the low-frequency librational mode has been much less studied with SFG. Because this mode is sensitive to the hydrogen-bond connectivity, understanding the librational mode of the interfacial water is crucial for unveiling a microscopic view of the interfacial water. Here, we compu…
Vibrational spectral studies of methyl 3-(4-methoxyphenyl)prop-2-enoate, a new organic non-linear optic crystal
2005
Single crystals of methyl 3-(4-methoxyphenyl)prop-2-enoate were grown by the slow evaporation technique and vibrational spectral analysis was carried out using near-IR Fourier transform Raman and Fourier transform IR spectroscopy. Ab initio quantum computations were also performed at the HF/6–311G (d,p) level to derive the equilibrium geometry, vibrational wavenumbers and intensities and first hyperpolarizability. The large NLO efficiency predicted for the first time in this new class of compounds was confirmed by powder efficiency experiments. Hartree–Fock calculations reveal that the endocyclic angle at the junction of the propeonate group and the phenyl ring is decreased from 120° by 2.5…
Temperature measurement in gas mixtures by femtosecond Raman-induced polarization spectroscopy
2003
The potential of femtosecond Raman-induced polarization spectroscopy (RIPS) for the simultaneous determination of temperature and concentrations was investigated. These measurements were related to the rotational time response of the molecular gas mixture, which was measured as a function of the pump-probe time delay. The change of the polarizability anisotropy with respect to the vibrational levels was taken into account. The results of temperature measurements in pure CO2 showed good agreement with the values obtained by a thermocouple. The RIPS technique was also applied to a CO2-N2 gas mixture to determine simultaneously temperatures and concentrations at temperatures up to 600 K. The a…