Clocking Enhanced Ionization of Hydrogen Molecules with Rotational Wave Packets

Area of Science:

• Molecular Physics
• Quantum Dynamics
• Laser Spectroscopy

Background:

• Laser-induced rotational wave packets provide insights into molecular dynamics.
• Understanding dissociation channels is crucial for controlling chemical reactions.

Purpose of the Study:

• To experimentally measure real-time rotational wave packets of H2 and D2.
• To investigate the time delay between dissociation channels.
• To demonstrate a novel "rotational clock" for molecular fragmentation.

Main Methods:

• Utilizing two sequential 25-fs laser pulses.
• Employing a reaction microscope for experimental measurements.
• Analyzing time-dependent yields of above-threshold dissociation and enhanced ionization.

Main Results:

• Observed a few-femtosecond time delay between dissociation channels for H2 and D2.
• Reproduced the observed delay using a classical model incorporating enhanced ionization.
• Demonstrated the ability to resolve sub-rotational dissociation dynamics.

Conclusions:

• The measured time delay is attributed to enhanced ionization and additional laser pulse interaction.
• The "rotational clock" concept is validated for resolving ultrafast molecular dynamics.
• This approach is generalizable to sequential fragmentation processes in other molecules.