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Salt Lake, India

Chatterjee S.,Bidhannagar College | Saha A.,Visva Bharati University | Talukdar B.,Visva Bharati University
Acta Physica Polonica A

We study revival and fractional revival phenomena of wave packets in a one-dimensional Rydberg atom irradiated by two time-delayed half-cycle pulses using an autocorrelation function characterized by electronic transition probabilities as weighting factors rather than modeling them by a Gaussian or Lorentzian distribution. If the momentum (q2) delivered to the atom by the second kick is much smaller than that (q1) imparted by the first one, the times of revival and fractional revival coincide with those of the single kicked atom. For q2 ≥ q1/4 appearance of revival and fractional revival depends on both the values of q2 and time delay t1 between the pulses but more sensitively on t1. The number of fractional revivals tends to become numerous as the value of t1 increases. Source

Talukdar D.,Saha Institute of Nuclear Physics | Chakraborty R.K.,Bidhannagar College | Bose S.,Saha Institute of Nuclear Physics | Bardhan K.K.,Saha Institute of Nuclear Physics
Review of Scientific Instruments

A low noise constant current source used for measuring the 1f noise in disordered systems in ohmic as well as nonohmic regime is described. The source can supply low noise constant current starting from as low as 1 A to a few tens of milliampere with a high voltage compliance limit of around 20 V. The constant current source has several stages, which can work in a standalone manner or together to supply the desired value of load current. The noise contributed by the current source is very low in the entire current range. The fabrication of a low noise voltage preamplifier modified for bias dependent noise measurements and based on the existing design available in the MAT04 data sheet is also described. © 2011 American Institute of Physics. Source

Chatterjee S.,Bidhannagar College
Physica Scripta

For a one-dimensional atom, we derive an exact analytical expression for the uncertainty product of a Rydberg wave packet (WP) produced by the impact of two time-delayed half-cycle pulses (HCPs) and use the result to study the problems of its (WP's) phase-space localization. We also investigate how to effectively use the second HCP to increase the atomic ionization probability. The time delay (t 1) between the two HCPs plays a crucial role in both cases. The values of t 1 can be chosen for the second HCP to kick the WP when the latter is near the inner or outer turning point. We found that long-lived localized states are produced by the impact of the second HCP only when the WP is near the inner turning point. In the same situation, if the electron is kicked away from the nucleus, the atomic ionization probability tends to a maximum. © 2012 The Royal Swedish Academy of Sciences. Source

Chatterjee S.,Bidhannagar College | Saha A.,Visva Bharati University | Talukdar B.,Visva Bharati University
Pramana - Journal of Physics

We present a quantum mechanical model to study the ionization of quasionedimensional Rydberg atoms interacting with half-cycle pulses (HCPs) and use it to demonstrate the inadequacy of semiclassical approaches to calculate ionization probabilities of such atoms subject to the impact of more than one HCP. For a single-kicked atom both models correctly reproduce the experimentally observed 's-curve' as can be seen by plotting the ionization probability P as a function of momentum transfer q1. We demonstrate that for a twice-kicked atom, the semiclassical model yields numbers for P which are not physically realizable. For fixed values of momentum transfers q1 and q2, in a twice-kicked atom, the ionization probability as a function of time delay between the kicks exhibits periodic decay and revival. The results of the semiclassical approach appear to agree with the quantum mechanical values at the times of revival of P, else these show considerable deviation. We attempt to provide a physical explanation for the limitation of the semiclassical approach. © 2016 Indian Academy of Sciences. Source

Saha A.,Visva Bharati University | Talukdar B.,Visva Bharati University | Chatterjee S.,Bidhannagar College
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

The Gardner equation ut+auux+bu2ux+μuxxx=0 is a generic mathematical model for weakly nonlinear and weakly dispersive wave propagation when the effects of higher-order nonlinearity become significant. Using the so-called traveling wave ansatz u(x,t)=φ(ξ), ξ=x-vt (where v is the velocity of the wave) we convert the (1+1)-dimensional partial differential equation to a second-order ordinary differential equation in with an arbitrary constant and treat the latter equation by the methods of the dynamical systems theory. With some special attention on the equilibrium points of the equation, we derive an analytical constraint for admissible values of the parameters a, b, and μ. From the Hamiltonian form of the system we confirm that, in addition to the usual bright soliton solution, the equation can be used to generate three different varieties of internal waves of which one is a dark soliton recently observed in water [A. Chabchoub, Phys. Rev. Lett. 110, 124101 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.124101]. © 2014 American Physical Society. Source

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