Editor-in-Chief : V.K. Rastogi
|AJP||ISSN : 0971 – 3093
Vol 12, No 1, January – March, 2003
Journal of Physics
Vol 12, No 1, January – March, 2003
Vol. 12, No 1 (2003) 1-12
Probing Molecular Dynamics by Femtosecond Time-Resolved Coherent Anti Stokes Raman Spectroscopy
M Schmitt1, T Siebert1, A S Grabtchikov2, V. Orlovich2, and W Kiefer1
1Institut fur Physikalische Chemie, Universität Wurzburg,
Am Hubland, D-97074 Wurzburg, Federal Republic of Germany
2B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus
Femtosecond time-resolved CARS spectroscopy is applied in order to prepare and monitor coherent states of different samples. The time evolution prepared by such methods gives information on the dynamics of molecular vibrations. In a first example the electronic ground state dynamics of biologically relevant porphyrin molecules are studied with transient CARS spectroscopy. Second, we report on selective excitation of the vibrational modes in the electronic ground state of polymers of diacetylene by means of a femtosecond time-resolved CARS scheme. Control is achieved by varying the timing and the phase shape (chirp) of the exciting laser pulses. Finally the capability of the CARS process to interrogate individual normal modes was utilised for exploring the influence of nuclear dynamics on the process of the S1/S0 internal conversion (IC) in 13-carotene, by placing the CARS process in a pump-probe scheme, where it plays the role of a mode selective probe.
Total Refs: 65
Vol. 12, No 1 (2003) 63-66
Studies of Christiansen effect on powdered glass using laser
R Changmai, R Mahanta and G D Baruah,
Department of Physics, Dibrugarh University, Dibrugarh-786 004, India
An experiment to demonstrate Christiansen effect is performed with irregular fragments of glass with He-Ne laser. Fifty colour photographs have been obtained using benzene, xylene and accetone as liquids under which the glass is immersed. Experiment have also been performed with spherical particles. This effect was demonstrated in 1884 by Christiansen who used powdered glass and put them inside a flat sided cell which is then filled with liquid and the refractive index of the latter was adjusted suitably by varying its composition. Beautiful chromatic effects are observed when the refractive index of the liquid is thus brought into coincidence with that of the powder for some chosen wavelength of the specutrum. This effect has been performed by laser light and photographs have been obtained on colour films for the first time. During the course of the experiments it has been observed that the cell becomes opaque for a restricted region of the cell in the vicinity where the surfaces of the two liquids meet. The cell becomes again selectively illuminated when the laser beam is incident at the boundary Separating the two liquids. © Anita Publications. All rights reserved.
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Vol. 12, No 1 (2003) 143-152
Collocation method for numerical scalar wave propagation through optical waveguiding structure
Physics Department, Indian Institute of Technology Delhi
NEW DELHI – 110 016, India
Email: [email protected]
Collocation method has been developed as a method which can treat the paraxial as well as non-paraxial wave propagation through optical waveguiding structures. The method, based on the orthogonal collocation principle, converts the Helmholtz equation into a matrix ordinary differential equation. This equation termed as the collocation equation can be solved either by using direct numerical techniques or by special techniques based on the matrix operator algebra. In the present paper, we outline the basic principle of the method and discuss its applications to the propagation of paraxial, wide-angle, bidirectional and nonlinear waves. Examples have also been included to show performance of the method.
Total Refs : 36