Dimer photofragmentation and cation ejection dynamics in helium nanodroplets

Area of Science:

• Physical Chemistry
• Chemical Physics
• Ultrafast Spectroscopy

Background:

• Helium nanodroplets (He_N) are weakly interacting systems ideal for studying isolated molecules.
• Indium dimers (In₂) are model systems for investigating electronic and vibrational dynamics.

Purpose of the Study:

• To investigate the ultrafast dynamics of indium dimers (In₂) solvated in helium nanodroplets (He_N) using femtosecond pump-probe spectroscopy.
• To elucidate the ionization and fragmentation pathways of In₂ within He_N.

Main Methods:

• Femtosecond pump-probe photoionization experiments.
• Covariance detection of ejected ions and photoelectrons.
• Solvation of indium dimers in helium nanodroplets.

Main Results:

• Observation of unexpected ejection of InHe_n⁺ ions (n=1-30) from He_N droplets following In₂ excitation.
• Identification of the ionization pathway as absorption-ionization-dissociation (AID).
• Revealing vibrational wave packet motion in neutral In₂* via the InHe_n⁺ signal.

Conclusions:

• The kinetic energy released during In₂ fragmentation allows ions to overcome the He_N binding potential.
• Electron-ion covariance detection provides a powerful tool for assigning ionization pathways in complex systems.
• This method offers a complementary observable for studying ultrafast photochemical processes within helium nanodroplets.