Photothermal Imaging of Transient and Steady State Convection Dynamics in Primary Alkanes

This paper presents a photothermal spectroscopy technique that effectively images convective heat flow in molecular liquids resulting from localized laser-induced heating. The method combines aspects of thermal lensing and photothermal deflection. A high-energy infrared laser is used to induce a thermal lens in the sample, and a divergent visible laser is used to probe the entire region of the excitation beam within the sample. This approach allows for the observation of the convective flow of the liquid above the excitation beam. The study focuses on the liquid primary alkanes, from n-pentane to n-pentadecane. The paper provides experimental results, including dynamical data for the propagation of the thermal plume, a transient feature, in these alkanes and the exploration of dependence on excitation laser power.