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Unraveling the Molecular Dependence of Femtosecond Laser-induced Thermal Lens Spectroscopy in Fluids

Abstract

Fluid systems exhibit thermal lens effects due to laser irradiation accompanied by convection in contrast primarily conductive heat dissipation in solids. The presence of a significant convective mode modifies the temperature gradient in fluids resulting in a deviation of the experimental results from theories that are based on pure conduction. Herein, we present a carefully designed femtosecond laser experiment that keeps the heat generation process constant in order to account for the effect of molecular properties on thermal dissipation. We derive a theoretical model that introduces and characterizes the additional convective heat transfer in thermal lens (TL) spectroscopy which explains our observed experimental results. We measured the TL signal for a series of liquid aliphatic alkanes, ranging from hexane to decane, and their comparison has proven the validity of our model. The influence of convective heat transfer in the TL signal is predicted in terms of the dimensionless Peclet number (PE). The lower values of PE for alkanes with longer carbon chains indicate that the convective flow of heat slows down substantially for larger molecules.

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Publication details

The article was received on 12 Jun 2019, accepted on 04 Nov 2019 and first published on 05 Nov 2019


Article type: Paper
DOI: 10.1039/C9AN01082C
Analyst, 2019, Accepted Manuscript

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    Unraveling the Molecular Dependence of Femtosecond Laser-induced Thermal Lens Spectroscopy in Fluids

    S. Singhal and D. Goswami, Analyst, 2019, Accepted Manuscript , DOI: 10.1039/C9AN01082C

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