Praveen Kumar

Instruments Research & Development Establishment

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Bill Poirier

Texas Tech University

Mahesh Kumar

Council of Scientific and Industrial Research

S. M. Shivaprasad

Jawaharlal Nehru Centre for Advanced Scientific Research

S. M. Shivaprasad

Jawaharlal Nehru Centre for Advanced Scientific Research

Jacek Kłos

University of Maryland, College Park

Hua Guo

University of New Mexico

Millard H. Alexander

University of Maryland, College Park

Bin Jiang

University of Science and Technology of China

B. R. Mehta

Indian Institute of Technology Delhi

Svetlana Malinovskaya

Stevens Institute of Technology

Cooperative Institutions

CSIR National Physical Laboratory of India

Jawaharlal Nehru Centre for Advanced Scientific Research

Centre National de la Recherche Scientifique

University College London

Eötvös Loránd University

National Physical Laboratory

Max Planck Institute of Microstructure Physics

University of Maryland, College Park

University of New Mexico

Vrije Universiteit Amsterdam

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Optimal control of multilevel quantum systems in the field-interaction representation

Physical Review A (2014)

Praveen Kumar Svetlana Malinovskaya Vladimir S. Malinovsky

A control strategy incorporating a fixed carrier frequency constraint on the optimal field is presented. As an illustrative example we consider the creation of maximum coherence in a six-level $\ensuremath{\Lambda}$ system by solving the Schr\"odinger equation without the rotating-wave approximation in the field-interaction representation. We demonstrate that application of the optimal control theory optimization reformulated in the field-interaction representation allows one to keep the carrier frequency of the control field constant and successfully optimize off-resonant processes in multilevel quantum systems.

Representation

10.1103/physreva.90.033427

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Citations (7)

Final State Resolved Quantum Predissociation Dynamics of SO₂(C̃¹B₂) and Its Isotopomers via a Crossing with a Singlet Repulsive State

The Journal of Physical Chemistry A (2017)

Changjian Xie Bin Jiang Jacek Kłos Praveen Kumar Millard H. Alexander

The fragmentation dynamics of predissociative SO2(C̃1B2) is investigated on an accurate adiabatic potential energy surface (PES) determined from high level ab initio data. This singlet PES features non-C2v equilibrium geometries for SO2, which are separated from the SO(X̃3Σ-) + O(3P) dissociation limit by a barrier resulting from a conical intersection with a repulsive singlet state. The ro-vibrational state distribution of the SO fragment is determined quantum mechanically for many predissociative states of several sulfur isotopomers of SO2. Significant rotational and vibrational excitations are found in the SO fragment. It is shown that these fragment internal state distributions are strongly dependent on the predissociative vibronic states, and the excitation typically increases with the photon energy.

Isotopomers

Conical intersection

Potential energy surface

Fragmentation

Kinetic isotope effect

10.1021/acs.jpca.7b04629

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Accurate characterization of the lowest triplet potential energy surface of SO2 with a coupled cluster method

The Journal of Chemical Physics (2019)

Praveen Kumar Jacek Kłos Bill Poirier Millard H. Alexander Hua Guo

The near-equilibrium potential energy surface (PES) of the ã 3B1 state of SO2 is developed from explicitly correlated spin-unrestricted coupled cluster calculations with single, double, and perturbative triple excitations with an augmented triple-zeta correlation-consistent basis set. The lowest-lying ro-vibrational energy levels of several sulfur isotopologues have been determined using this PES. It is shown that the new ab initio PES provides a much better description of the low-lying vibrational states than a previous PES determined at the multi-reference configuration interaction level. In particular, the theory-experiment agreement for the three lowest-lying vibrational transitions is within 1–3 cm−1.

Coupled cluster

Potential energy surface

Isotopologue

10.1063/1.5088959

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Residual thermal desorption studies of Ga adatoms on trenched Si(5512) surface

Applied Surface Science (2013)

Praveen Kumar Mahesh Kumar S. M. Shivaprasad

Thermal desorption

Thermal Stability

Surface reconstruction

Atmospheric temperature range

10.1016/j.apsusc.2013.05.132

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Citations (3)

Design of Optimal Laser Fields to Control Vibrational Excitations in Carboxy-myoglobin

Lecture notes in computer science (2008)

Harjinder Singh Sitansh Sharma Praveen Kumar Jeremy N. Harvey Gabriel G. Balint‐Kurti

10.1007/978-3-540-69387-1_43

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First-principles C band absorption spectra of SO₂ and its isotopologues

The Journal of Chemical Physics (2017)

Bin Jiang Praveen Kumar Jacek Kłos Millard H. Alexander Bill Poirier

The low-energy wing of the C∼B21←X∼1A1 absorption spectra for SO2 in the ultraviolet region is computed for the 32S,33S,34S and 36S isotopes, using the recently developed ab initio potential energy surfaces (PESs) of the two electronic states and the corresponding transition dipole surface. The state-resolved absorption spectra from various ro-vibrational states of SO2(X∼1A1) are computed. When contributions of these excited ro-vibrational states are included, the thermally averaged spectra are broadened but maintain their key characters. Excellent agreement with experimental absorption spectra is found, validating the accuracy of the PESs. The isotope shifts of the absorption peaks are found to increase linearly with energy, in good agreement with experiment.

Isotopologue

Kinetic isotope effect

Isotopic shift

10.1063/1.4980124

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Citations (7)

Publisher’s Note: “New ab initio adiabatic potential energy surfaces and bound state calculations for the singlet ground X̃1A1 and excited C̃1B2(21A′) states of SO₂” [J. Chem. Phys. 144, 174301 (2016)]

The Journal of Chemical Physics (2016)

Jacek Kłos Millard H. Alexander Praveen Kumar Bill Poirier Bin Jiang

First Page

Singlet fission

10.1063/1.4951737

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Citations (1)

( 7 × 7 ) reconstruction as barrier for Schottky-barrier formation at the Ga/Si(111) interface

Applied Physics Letters (2010)

Praveen Kumar Mahesh Kumar S. M. Shivaprasad

We report the change in electronic properties of the Ga/Si interface by monitoring the Ga(3d) core-level photoelectron spectra and electron diffraction induced by submonolayer Ga adsorption on Si(111)-7×7 surface. The spectra shows a flat band for submonolayer coverages, attributed to the metallic nature of the Si(111)-7×7 reconstruction and a premetallic band structure of two-dimensional Ga islands. At 1 ML, electron diffraction pattern shows metallic (7×7) to semiconducting (1×1) phase-transition and the spin-orbit split branching ratio of Ga(2p) core level attain the metallic bulk value, and the barrier assumes the Schottky–Mott value while full width half maxima and branching ratio attain bulk values.

Surface reconstruction

10.1063/1.3490250

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FORMATION OF ONE-DIMENSIONAL Ga STRUCTURES ON Si(5 5 12)-2 × 1 TRENCHED TEMPLATES

International Journal of Nanoscience (2011)

Praveen Kumar Mahesh Kumar Govind Govind B. R. Mehta S. M. Shivaprasad

In the advent of GaN photonic devices, there is renewed interest in looking at the growth of nanostructures of III-Nitrides that can yield novel properties. To grow a high density of self-assembled GaN nanostructures on a large scale, there is a need to use templates with well-defined nanometer scale features. The Si (5 5 12)-2 × 1 surface is a naturally faceted stable surface that has several nanotrenches of (225) and (337) with a large unit cell of 5.35 × 0.77 nm 2 . In this work we present here, the first report on the X-ray photoelectron spectroscopy study of the adsorption kinetics of Ga on Si (5 5 12)-2 × 1 reconstructed surface. The uptake curve which is the plot of the ratio of Ga (2 p ) to Si (2 p ) intensity with deposition time, shows that Ga grows in a Stranski–Krastnov growth mode on Si (5 5 12) surface. The core level spectra of Si (2 p ) and Ga (2 p ) have been deconvoluted to see the evolution of the interface during the adsorption process of Ga . The valence-band spectra show the modification of the electronic structure and the secondary electron emission spectra yield the change in work function during Ga adsorption. Correlating the electronic and structural aspects of the interface formation results the study demonstrates the possibility of integrating Si and group III-nitride technologies while exploiting the novel properties due to reduced dimensions.

Template

Nanometre

10.1142/s0219581x11007491

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A superstructural 2D-phase diagram for Ga on the Si(111)- 7x7 system

Solid State Communications (2011)

Praveen Kumar Jithesh Kuyyalil Mahesh Kumar S. M. Shivaprasad

Auger electron spectroscopy

Low-energy electron diffraction

10.1016/j.ssc.2011.08.033

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Citations (9)