Photoionization study of multiphoton-excited SF6 in a molecular beam

Area of Science:

• Physical Chemistry
• Molecular Spectroscopy
• Laser-Induced Chemistry

Background:

• Understanding molecular excitation dynamics is crucial for controlling chemical reactions.
• Sulfur hexafluoride (SF6) is a molecule extensively studied for its response to infrared laser absorption.
• The quasi-continuum model describes highly excited molecular states relevant to dissociation.

Purpose of the Study:

• To investigate the vibrational-energy distribution of SF6 molecules under intense CO2 laser irradiation.
• To determine the extent of excitation into the quasi-continuum near the dissociation threshold.
• To identify and characterize the bottleneck effect in molecular laser excitation.

Main Methods:

• Molecular-beam photoionization technique used to probe excited SF6 molecules.
• Excitation achieved using an intense CO2 laser.
• Experiments conducted at laser energy fluences near and below the dissociation threshold.

Main Results:

• A significant bottleneck in vibrational excitation was observed at low laser intensities.
• Even near the dissociation threshold, most SF6 molecules remained in discrete energy levels.
• Only a small fraction (10-25%) of molecules were excited into the quasi-continuum.

Conclusions:

• The bottleneck effect significantly hinders the excitation of SF6 molecules into the quasi-continuum.
• Laser intensity plays a critical role in overcoming the bottleneck and achieving higher excitation levels.
• These findings have implications for understanding and controlling laser-induced dissociation processes.