Femtosecond Dynamics of Ionized Molecular Systems

Femtosecond dynamics of ionized molecular systems explores how molecules respond when stripped of an electron on timescales shorter than 10^–15 seconds. In these ultrafast regimes, the interplay between electronic excitation and nuclear motion gives rise to coherent vibrational wave packets, nonadiabatic transitions and rapid fragmentation pathways. By employing tailored laser pulses, researchers can resolve the birth and evolution of radical cations, observe bond stretching and bending in real time, and even steer molecular dissociation. Such insights illuminate fundamental processes in photochemistry, radiation damage to biomolecules and the initiation of energetic materials. The temporal precision of pump–probe schemes and the sensitivity of time-resolved mass spectrometry or high harmonic spectroscopy have transformed our understanding of how ionization induces electronic redistribution, vibrational coherence and chemical transformation. These discoveries underpin applications ranging from selective bond breaking in complex organic molecules to the design of safer explosives and the development of novel light-driven catalysts.

Research from Nature Portfolio

Recent studies have demonstrated that a combination of femtosecond laser mass spectrometry and high harmonic spectroscopy can distinguish structural isomers through their ionisation and recombination dynamics. Transform-limited pulses of varying polarisation were used to induce and probe double ionisation in xylene isomers, revealing distinct trends in doubly charged ion yields as the laser polarisation was rotated. Concurrently, high harmonic generation measurements exposed isomer-specific variations in photo-recombination efficiency. Together, these techniques provided a powerful route to fingerprint molecular structure via ultrafast electron dynamics and offered a template for extending coherent spectroscopy to more complex organic systems.

Femtosecond Dynamics of Ionized Molecular Systems publication trend

The graph below shows the total number of articles in femtosecond dynamics of ionized molecular systems across all publications each year (not limited to Nature Index journals).

Technical terms

Femtosecond time-resolved mass spectrometry: A method that uses ultrashort laser pulses to ionise molecules and record fragment ions with femtosecond temporal resolution.

Pump–probe spectroscopy: A technique in which one laser pulse (pump) initiates dynamics and a second (probe) interrogates the evolving system after a controlled delay.

Radical cation: A positively charged ion formed by removal of an electron, often exhibiting distinct electronic and vibrational dynamics.

Vibrational wave packet: A coherent superposition of vibrational eigenstates that propagates on a potential energy surface.

Nonadiabatic dynamics: Electronic transitions that occur when nuclear motion drives the system through regions of strong coupling between electronic states.

High harmonic generation: A nonlinear optical process in which intense laser fields drive an electron to recombine with its parent ion, emitting high-order harmonics of the driving frequency.

References

1. Coherent Control of Molecular Dissociation by Selective Excitation of Nuclear Wave Packets. Frontiers in Chemistry (2022).
2. Femtosecond Laser Mass Spectrometry and High Harmonic Spectroscopy of Xylene Isomers. Scientific Reports (2018).
3. Photodissociation Dynamics of the Highly Stable ortho-Nitroaniline Cation. The Journal of Physical Chemistry A (2024).
4. Ultrafast Dissociation Dynamics of the Sensitive Explosive Ethylene Glycol Dinitrate. The Journal of Physical Chemistry Letters (2025).
5. Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry. Molecules (2019).