Articles written in Pramana – Journal of Physics

    • Vibrational energy transfer in a collinear HF-HF collision involving low-lying states in the presence of infrared laser beam

      Bhupat Sharma Vinod Prasad Man Mohan

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      An approximate method for the vibration-vibration (V-V) energy transfer process during collinear collisions of two HF molecules involving low-lying states in the presence of infrared laser beam using a quasi-energy approach (non-perturbative) is presented. The effect of radiation on V-V process is investigated by changing the laser field detuning and power for various values of collision velocities.

    • Interaction of strong laser beam with He-atom using non-perturbative Floquet method

      Man Mohan Vinod Prasad Bhupat Sharma

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      Non-perturbative Floquet method is used to investigate the interaction of strong linearly polarized light with He-atom. In the calculations, six lowest singlet target states and fifteen photon states are taken for absolute convergence. For allowed transitions, accurate oscillator strengths using configuration interaction wave-functions are used. A number of interesting features such as nonlinear effects at high intensities, line broadening, a dynamic Stark effect are obtained and explained.

    • Photoionization of the ground1Se and twenty lowest excited states of the Ne-like Fe16+

      M Mohan M Le Dourneuf Vinod Prasad A Kumar

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      TheR-matrix method is used to calculate cross-sections for the photoionization of Ne-like Fe16+ from ground 2s22p61Se and excited states belonging to 2s2p6 3l and 2s22p5 3l configurations. Configuration interaction wavefunctions are used to represent two target states of Fe17+ ion retained in theR-matrix expansion. The cross-sections are obtained as a function of kinetic energy (εk) of the ejected electron from 10 to 24 Ry. For low kinetic energy the cross-sections show series of Rydberg states which converge onto2Se threshold Fe17+. The calculations are carried out in the LS coupling.

    • Ultrashort laser pulse suppression of dissociation in a molecule

      Man Mohan Vinod Prasad Rinku Sharma

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      Effect of laser pulse in suppressing the dissociation of a molecule is shown. The time dependent Schrödinger is solved numerically for a molecule in an intense laser pulse whose uppermost state is connected to continuum.

    • Quantum ring states in magnetic field and delayed half-cycle pulses


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      The present work is dedicated to the time evolution of excitation of a quantum ring in external electric and magnetic fields. Such a ring of mesoscopic dimensions in an external magnetic field is known to exhibit a wide variety of interesting physical phenomena. We have studied the dynamics of the single electron quantum ring in the presence of a static magnetic field and a combination of delayed half-cycle pulse pair. Detailed calculations have been worked out and the impact on dynamics by variation in the ring radius, intensity of external electric field, delay between the two pulses, and variation in magnetic field have been reported. A total of 19 states have been taken and the population transfer in the single electron quantum ring is studied by solving the time-dependent Schrödinger equation (TDSE), using the efficient fourth-order Runge--Kutta method. Many interesting features have been observed in the transition probabilities with the variation of magnetic field, delay between pulses and ring dimensions. A very important aspect of the present work is the persistent current generation in a quantum ring in the presence of external magnetic flux and its periodic variation with the magnetic flux, ring dimensions and pulse delay.

    • Pressure- and temperature-dependent EIT studies in a parabolic quantum dot coupled with excitonic effects in a static magnetic field


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      The present paper analyses the electromagnetically-induced transparency (EIT) in a three-level ladder type system in an excitonic three-dimensional quantum dot (QD) with a parabolic potential in the presence of astatic magnetic field, a resonant probe field and a coupler field. Eigen values, wave functions, dipole matrix elementsand selection rules of the quantum system are calculated analytically within the effective mass approximation bysolving the corresponding Schrödinger equation and taking into consideration both the confinement and Coulomb potentials of the electron–hole pair. To illustrate the interaction with the optical fields, the analytical expressions forthe complex electric susceptibility, absorption, dispersion, group index (GI) and the combined effects of external factors such as magnetic field, hydrostatic pressure, temperature and dimensions of the QD are examined

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