Sub-7-femtosecond conical-intersection dynamics probed at the carbon K-edge

Area of Science:

• * Physical Chemistry
• * Molecular Spectroscopy
• * Ultrafast Dynamics

Background:

• * Conical intersections are crucial for de-excitation pathways in electronically excited molecules.
• * Understanding ultrafast electronic relaxation is key to controlling molecular behavior.
• * Previous spectroscopic methods limited the observation of these rapid processes.

Purpose of the Study:

• * To measure the fastest electronic relaxation dynamics to date.
• * To probe the dynamics of ethylene cations (C2H4+) at the carbon K-edge.
• * To demonstrate the capability of attosecond transient-absorption spectroscopy (ATAS) for ultrafast molecular studies.

Main Methods:

• * Utilized attosecond transient-absorption spectroscopy (ATAS) extended to the carbon K-edge.
• * Selectively initiated wave packets in the D0 and D1 electronic states of C2H4+.
• * Analyzed spectral separation of D1 and D0 bands attributed to electron correlation.

Main Results:

• * Observed electronic relaxation from the D1 to D0 state in C2H4+ with a time constant of 6.8 ± 0.2 femtoseconds.
• * Directly visualized electronic state switching via ATAS.
• * Simultaneously captured multidimensional structural dynamics of the molecule.

Conclusions:

• * Attosecond transient-absorption spectroscopy (ATAS) can resolve ultrafast electronic and structural dynamics in organic molecules.
• * Electronic relaxation in ethylene, a prototypical organic chromophore, occurs within a single vibrational period.
• * This technique opens new avenues for studying rapid molecular processes.