Ultrafast charge transfer and atomic orbital polarization

Area of Science:

• Surface science
• Ultrafast spectroscopy
• Quantum chemistry

Background:

• Understanding charge transfer dynamics at surfaces is crucial for catalysis and materials science.
• Orbital orientation of adsorbates plays a key role in surface interactions.

Purpose of the Study:

• To investigate the influence of orbital polarization on ultrafast charge transfer between an atomic adsorbate and a substrate.
• To measure charge transfer times for different spatial orientations of adsorbate resonance states.

Main Methods:

• Core hole clock spectroscopy using linearly polarized X-ray radiation.
• Selective excitation of adsorbate resonance states with defined spatial orientation.
• Study of the c(4 x 2)S/Ru(0001) system.

Main Results:

• Charge transfer times were measured for two distinct sulfur 2s(-1)3p* resonance states.
• Excitation to the 3p perpendicular* state (surface normal) resulted in a charge transfer time of 0.18 ± 0.07 fs.
• Excitation to the 3p parallel* state (surface plane) resulted in a charge transfer time of 0.84 ± 0.23 fs.

Conclusions:

• Orbital polarization directly influences ultrafast charge transfer rates.
• The observed variation in charge transfer times is attributed to differences in adsorbate-substrate orbital overlap.
• This study provides insights into controlling electron transfer dynamics at interfaces.