Heating anomaly of cold interfacial water under irradiation of mid-infrared pulses

TL;DR

This study uses molecular dynamics simulations to reveal that mid-infrared pulses cause a larger temperature increase in interfacial water at lower initial temperatures, due to enhanced vibrational transition efficiency.

Contribution

It uncovers the mechanism behind the anomalous heating of interfacial water under mid-infrared irradiation, highlighting the role of molecular orientation and vibrational transitions.

Findings

Lower initial temperature water exhibits larger temperature jumps under IR irradiation.

Enhanced asymmetric OH stretching transition efficiency explains the anomaly.

Interfacial water properties are highly sensitive to initial temperature.

Abstract

The mid-infrared heating of interfacial water with different initial temperatures is studied using non-equilibrium molecular dynamics simulation. It is found that under the irradiation of a pulse at 3360-3380 $cm^{-1}$ the two-dimensional water monolayer on a hydrophilic surface at a lower initial temperature acquires a much larger temperature jump. The mechanism beneath this counterintuitive phenomenon is the enhanced transition efficiency of the asymmetric OH stretching vibration due to the specific oriented configuration of water molecules at lower initial temperatures. The understanding of the anomalous phenomenon clarifies the sensitivity of the interfacial properties of water molecules to the temperature.