State-Resolved Probing of Attosecond Timescale Molecular Dipoles

Area of Science:

• Quantum Chemistry
• Attosecond Spectroscopy
• Molecular Dynamics

Background:

• Attosecond transient absorption spectroscopy (ATAS) probes ultrafast electronic dynamics.
• Core-level spectroscopy provides element-specific insights into molecular electronic structure.
• Understanding light-matter interactions in molecules is crucial for controlling chemical reactions.

Purpose of the Study:

• To experimentally investigate iodomethane using ATAS in the iodine 4d core-excitation region.
• To differentiate the ATAS signatures of core-to-valence and core-to-Rydberg excitations in molecules.
• To elucidate the influence of near-infrared (NIR) fields on molecular electronic states.

Main Methods:

• Experimental attosecond transient absorption spectroscopy (ATAS) using extreme ultraviolet (XUV) and near-infrared (NIR) pulses.
• Spectroscopic analysis of delay-dependent absorbance changes.
• Ab initio calculations and ATAS simulations for theoretical validation.

Main Results:

• Observed light-induced phase shifts and pathway interferences in XUV-NIR ATAS of iodomethane.
• Identified distinct ATAS signatures for core-to-valence versus core-to-Rydberg excitations.
• Demonstrated dominant NIR field effects on core-to-Rydberg states, unlike core-to-valence states.

Conclusions:

• Molecular ATAS reveals unique behaviors of valence and Rydberg states under NIR fields.
• Core-to-Rydberg states are more sensitive to moderately strong, nonionizing NIR fields.
• Experimental and theoretical results provide a comprehensive understanding of light-induced dynamics in iodomethane.