Settling time of a vibrational wavepacket in ionization.

Area of Science:

• Quantum mechanics
• Molecular physics
• Physical chemistry

Background:

• The Franck-Condon principle typically assumes real amplitudes for vibrational wavefunctions during ionization.
• This implies zero phase for vibrational wavefunctions in the generated wavepacket.
• Previous models did not account for phase modulation in this context.

Purpose of the Study:

• To investigate the phase properties of vibrational wavepackets generated during molecular ion ionization.
• To experimentally observe deviations from the Franck-Condon principle regarding wavefunction amplitudes.
• To quantify the temporal effects of any observed phase modulation.

Main Methods:

• Generation of a vibrational wavepacket in the ground electronic state of H₂⁺.
• Ionization of the molecular ion.
• Time-resolved spectroscopic analysis to probe the wavepacket dynamics.
• Analysis of wavefunction amplitude phase modulation.

Main Results:

• Observation of a non-trivial phase modulation in the vibrational wavepacket amplitudes.
• The phase modulation leads to a group delay of approximately 1 femtosecond (fs) for specific vibrational states.
• This delay represents the settling time for the initial vibrational wavepacket.

Conclusions:

• The Franck-Condon principle's assumption of real amplitudes is insufficient for describing certain ionization processes.
• Phase modulation of vibrational wavefunctions is a key factor in the dynamics of molecular ion ionization.
• The observed group delay provides insights into the temporal evolution and composition of quantum wavepackets.