Combining dissociative ionization pump-probe spectroscopy and ab initio calculations to interpret dynamics and...

Area of Science:

• Molecular Dynamics
• Quantum Chemistry
• Ultrafast Spectroscopy

Background:

• Nonadiabatic processes significantly influence molecular dynamics, impacting molecular behavior and control.
• Nucleic acid bases, cytosine and uracil, exhibit rapid radiationless relaxation via conical intersections after UV absorption.
• Multiple relaxation pathways offer potential for controlling molecular dynamics.

Purpose of the Study:

• To investigate excited-state dynamics in cytosine and uracil using advanced computational and experimental techniques.
• To explore the possibility of controlling molecular pathways through targeted laser excitation and probing.
• To correlate molecular fragments and their dynamics with specific neutral relaxation pathways.

Main Methods:

• High-level electronic structure calculations to determine potential energy surfaces of neutral and ionic states.
• Excitation of molecules using deep UV ultrafast laser pulses.
• Probing molecular dynamics with strong-field near-infrared pulses for ionization and dissociation.
• Analysis of fragment dynamics to identify signatures of different neutral relaxation pathways.

Main Results:

• Different molecular fragments exhibit distinct dynamics, serving as signatures for various relaxation pathways.
• Multiconfigurational electronic structure methods successfully mapped potential energy surfaces.
• The study established a link between ionic fragmentation patterns and neutral excited-state dynamics.
• Identification of specific fragments correlating to distinct relaxation pathways was achieved.

Conclusions:

• The developed approach allows for the tracking of molecular dynamics by analyzing fragment signatures.
• This method provides insights into controlling nonadiabatic processes in biologically relevant molecules.
• Potential strategies for controlling molecular dynamics through laser manipulation were discussed.