Chemistry

Time-resolved THz Stark spectroscopy of molecules in water

Elnaz Zyaee, Vladislav Slama, Seyyed Jabbar Mousavi, David Rohrbach, Ursula Rothlisberger, Thomas Feurer

Featured August 12, 2026

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Simply

Scientists found a new way to use super-fast light pulses (terahertz pulses) to measure how molecules in water react to electricity, even at room temperature, which helps understand how they work in real-life situations.

In depth

The paper presents the first successful application of Time-Resolved Terahertz Stark Spectroscopy (TRTSS) to molecules dissolved in water at room temperature, a highly challenging environment. By utilizing ultrafast THz pulses that are faster than molecular reorientation, the authors overcome limitations of conventional Stark methods, enabling the precise measurement of dipole moment changes and polarizabilities in aqueous solutions. This significantly expands the utility of Stark spectroscopy for understanding molecular electronic properties in their native, solvated state.

Key Takeaways

1
TRTSS is successfully demonstrated for the first time in water at room temperature, overcoming significant challenges posed by the solvent's strong absorption and dielectric screening.
2
The technique enables the quantitative extraction of molecular parameters like dipole moment changes ( $∣Δ μ ∣$ ) and polarizabilities (Tr( $Δ α$ )) in biologically relevant aqueous environments.
3
Comparison with TD-DFT calculations reveals that conformational effects and thermal fluctuations can significantly influence the extracted Stark parameters in solvated molecules.

Conceptual Flow

HIGH LEVEL

Methodology (The "Logic")

Instead of freezing samples, they use super-fast light pulses to zap molecules in water and see how their light absorption changes.

Molecules in Water

Zap with Fast Light

Measure Light Change

Results (The "Impact")

This new method successfully showed how molecules in water change their electric properties, which was impossible before, opening doors for new discoveries.

Old Method (Frozen)

Can't See in Water

New Method (Water)