Research Interests & Accomplishments:
Listed
counter-chronologically start-timewise:
The pursuit of
attosecond (10-18 sec) optical pulses continues unabatedly with the
basic aim of chasing electrons inside an atom, just as the high-speed
photography can capture an image of a bullet speeding through the air.
Propagation of ultrashort IR laser pulses through a noble gas leads to the
formation of single optical cycle pulses through a non-linear process called
filamentation. Interestingly, the intensity of the final pulse is automatically
clamped to the field ionization threshold. Utilizing this advantage we have let
a filamented pulse move through a noble gas medium to create single pulses of
attosecond duration via the higher order harmonic generation. Effects of
carrier-envelope-phase on the final pulse formation mechanism are being
investigated.
Resonant charge
transfer is an important process among several processes occurring during the
interaction of an ionic or a neutral species with a metal surface. Owing to the
sensitivity of the process to the electronic structure of the participating
candidates, it serves as a valuable probe to understand many salient structural
features, namely, the effect of electronic band gap on the transfer dynamics,
influence of surface symmetry and surface morphology, initial precursors to
catalytic reactions on the surface etc. Significant thrust is being geared to
understand the morphology of nanostructured surfaces by using anion beam as a
probe with a long term goal of creating "designer's nano-surface" to
catalize or de-catalize surface reactions as desired. We investigate this
process by using the Cranck-Nicholson wave-packet propagation technique.
Finite systems,
including atomic clusters, fullerenes, carbon nanotubes, and quantum dots are
interesting objects as they exhibit properties that hover between realms of the
single atom and the bulk. Contrary to the point-like atomic nucleus, a positive
ion-core with a certain spatial extension provides the primary binding for
valence electrons in such a system. As a result, these electrons delocalize
over the ion-core and, consequently, the effective electronic potential
acquires, in comparison to the atomic potential, a radically different shape: a
flat interior and a sharp edge. The influence of this delocalization on both
the single-electron and the collective phenomena is the focus of this topic.
Calculations are performed in the time-dependent density functional theory to
include electronic collectivity.
Interaction of a single
photon with an atom is an excellent ``laboratory'' to understand the effects of
many electron correlation. Possibility of precision measurements, owing to
advance generation synchrotron light sources worldwide, motivates extensive
theoretical work for detail understanding of the photo-processes. Also,
photoabsorption studies, particularly involving ions, have crucial importance
in numerous astrophysical applications. We employ the relativistic-random phase
approximation (RRPA) to calculate the non-resonant photospectra. The
autoionizing resonances are calculated by using the relativistic-multichannel
quantum defect theory with RRPA combined as an adjunct.