Laser control of an excited-state vibrational wave packet in neutral H$_2$

TL;DR

This study demonstrates the control of vibrational wave packets in excited neutral H₂ molecules using ultrafast laser pulses, revealing how NIR fields can modify quantum dynamics observable through XUV absorption spectra.

Contribution

It introduces a novel method for nonlocal-in-time laser control of molecular vibrational dynamics via XUV transient absorption spectroscopy.

Findings

NIR pulses significantly modify vibrational wave packet revivals.

Control is achieved with NIR pulses applied only 7 fs after wave packet creation.

The approach is broadly applicable to various molecules and materials.

Abstract

We observe and control a molecular vibrational wave packet in an electronically excited state of the neutral hydrogen molecule. In an extreme-ultraviolet (XUV) transient-absorption experiment we launch a vibrational wave packet in the $D ^1\Pi_u 3p\pi$ state of H$_2$ and observe its time evolution via the coherent dipole response. The reconstructed time-dependent dipole from experimentally measured XUV absorption spectra provides access to the revival of the vibrational wave packet, which we control via an intense near-infrared (NIR) pulse. Tuning the intensity of the NIR pulse we observe the revival of the wave packet to be significantly modified, which is supported by the results of a multi-level simulation. The NIR field is applied only 7 fs after the creation of the wave packet but influences its evolution up to at least its first revival at 270 fs. This experimental approach for nonlocal-in-time laser control of quantum dynamics is generally applicable to a large range of molecules and materials as it only requires the observation of absorption spectra.