Tracing molecular dynamics at the femto-/atto-second boundary through extreme-ultraviolet pump-probe spectroscopy

TL;DR

This paper demonstrates simultaneous tracking of vibrational and electronic dynamics in molecular hydrogen using broadband extreme-ultraviolet pulses, revealing ultrafast processes at the femto- and atto-second boundary with minimal disturbance.

Contribution

It introduces a method for coherently exciting and probing the full spectrum of H2 to observe ultrafast molecular dynamics on sub-femtosecond timescales.

Findings

Successful excitation of the entire H2 spectrum with broadband XUV pulses

Observation of vibrational, electronic, and ionization dynamics on 1 fs timescale

Minimal distortion of molecular potential during XUV probing

Abstract

Coherent light pulses of few to hundreds of femtoseconds (fs) duration have prolifically served the field of ultrafast phenomena. While fs pulses address mainly dynamics of nuclear motion in molecules or lattices in the gas, liquid or condensed matter phase, the advent of attosecond pulses has in recent years provided direct experimental access to ultrafast electron dynamics. However, there are processes involving nuclear motion in molecules and in particular coupled electronic and nuclear motion that possess few fs or even sub-fs dynamics. In the present work we have succeeded in addressing simultaneously vibrational and electronic dynamics in molecular Hydrogen. Utilizing a broadband extreme-ultraviolet (XUV) continuum the entire, Frank-Condon allowed spectrum of H2 is coherently excited. Vibrational, electronic and ionization 1fs scale dynamics are subsequently tracked by means of XUV-pump-XUV-probe measurements. These reflect the intrinsic molecular behavior as the XUV probe pulse hardly distorts the molecular potential.