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Abstract
Chemical transformations in molecules are a consequence of valence electron motion and its
eventual coupling to atomic motion, hence, tracking valence electron motion at the orbital
level is the key to understanding and taming such transformations. Scanning tunnelling
microscopy (STM) can passively and locally probe the valence electron density in
molecules. Contemporary techniques in attosecond science1,2
, on the other hand, can
generate and track the temporal evolution of a coherent superposition of quantum states of
valence electrons by using strong laser fields, which can be probed only non-locally. In
absence of the capability to trigger and probe electron dynamics at the single-orbital level,
electron motion could only be inferred by reconstruction. In the talk, I will show you how
dynamics of coherent superposition of valence electron states generated by < 6 femtosecond
long carrier-envelope-phase (CEP) stable laser pulses, can be locally probed with picometer
spatial resolution and 300 attosecond temporal resolution simultaneously, at the single
orbital-level with the help of an STM, defying the previously established fundamental space-
time limit3,4
. Near fields of optical pulses confined to the apex of nanotip of an STM enable
orbital imaging of electronic levels of molecules with pm resolution. We envisage that it will
be possible to see a chemical bond formation dynamics through a transition state at the orbital
level in the near future. |