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Ultrasensitive thermal lens (TL) spectroscopy, where the interplay between conduction and convection is crucial, provides profound insights into molecular behavior. This work focuses on the critical role of molecular convection by using the dual-beam z-scan method and time-resolved TL spectroscopy. We specifically investigated the correlation between the detection iris and the spot size of the pump beam. Additionally, we address detection limitations and their influence on the perception of convection timing. We introduce an experimentally derived ratio optimized for higher sensitivity, enhancing the reliability of TL spectroscopy. This refined approach to TL spectroscopy allows for a deeper exploration of molecular characteristics in liquids.
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http://dx.doi.org/10.1021/acs.jpca.4c04030 | DOI Listing |
Chem Asian J
June 2025
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
Femtosecond thermal lens spectroscopy (FTLS) is a powerful analytical tool, yet its application to complex, multi-component mixtures like fragrance accords remains limited. Here, we introduce and validate a unified metric, the femtosecond thermal lens integrated magnitude (FTL-IM), to characterize such mixtures. The FTL-IM, derived from the integrated signal area, provides a direct, model-free measure of the total thermo-optical response, including critical convective effects.
View Article and Find Full Text PDFJ Phys Chem A
October 2024
Centre for Lasers and Photonics, Indian Institute of Technology Kanpur, Kanpur 208016, India.
Ultrasensitive thermal lens (TL) spectroscopy, where the interplay between conduction and convection is crucial, provides profound insights into molecular behavior. This work focuses on the critical role of molecular convection by using the dual-beam z-scan method and time-resolved TL spectroscopy. We specifically investigated the correlation between the detection iris and the spot size of the pump beam.
View Article and Find Full Text PDFIn this work, we have introduced a Z-scan thermal lens (TL) model based on Laguerre-Gaussian (LG) 10 laser induced excitation in a mode-mismatched dual-beam configuration. The analytical expression of the TL signal and its dependence on sample to detector distance as well as the Z-scan have been derived. The theoretical analysis shows that the phase shift and TL signal are higher than the values obtained using an excitation with the Gaussian profile.
View Article and Find Full Text PDFMaterials (Basel)
January 2023
Department of Optoelectronics, University of Kerala, Trivandrum 695581, Kerala, India.
Ageing of engine oil is an important issue determining the engine life and performance. The present work attempts to delineate the ageing-induced changes in engine oil through the mode-mismatched dual-beam thermal lens (MMDBTL) technique and other conventional spectroscopic techniques. For the analyses, engine oil samples were collected after every 200 km of runtime.
View Article and Find Full Text PDFPulsed laser beam excitations are more commonly used in thermal lens spectroscopy (TLS) than continuous-wave (CW) ones, because CW excitations limit the measurement to linear absorption processes [J. Opt. A5, 256 (2003)].
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