Browsing by Author "Philip, R"

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    Ultrafast optical nonlinearity, electronic absorption, vibrational spectra and solvent effect studies of ninhydrin
    (PERGAMON-ELSEVIER SCIENCE LTD) Sajan, D; Devi, TU; Safakath, K; Philip, R; Nemec, I; Karabacak, M
    FT-IR, FT-Raman and UV-Vis spectra of the nonlinear optical molecule ninhydrin have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model. Natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Employing the open-aperture z-scan technique, nonlinear optical absorption of the sample has been studied in the ultrafast and short-pulse excitation regimes, using 100 fs and 5 ns laser pulses respectively. It is found that ninhydrin exhibits optical limiting for both excitations, indicating potential photonic applications. (C) 2013 Elsevier B.V. All rights reserved.
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    Multi-photon absorption effect and intra-molecular charge transfer of donor-π-acceptor chromophore ethyl p-amino benzoate
    (PERGAMON-ELSEVIER SCIENCE LTD) Sajan, D; Vijayan, N; Safakath, K; Philip, R; Karabacak, M
    Fourier transform (FT)-Raman and infrared (IR) spectra of the nonlinear optical (NLO) material ethyl p-amino benzoate (EPAB) have been recorded and analyzed. The geometry and harmonic vibrational wave-numbers are calculated with the help of B3LYP density functional theory method. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions leading to its NLO activity and charge delocalization have been analyzed using natural bond orbital (NBO) analysis. Employing the open-aperture z-scan technique, NLO absorption of the sample has been studied in two excitation regimes, using 100 fs and 5 ns laser pulses respectively. It is found that EPAB is a three-photon absorber for 100 fs pulses at the excitation wavelength of 800 nm. For ns pulses at 532 nm it exhibits strong optical limiting, indicating possible photonics applications. (C) 2013 Elsevier B.V. All rights reserved.