Interfacial optical absorptance of air-water interfaces

Fuente: arXiv
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Main Authors: Bohm, Preston, Li, Mingjun, Menon, Akanksha K., Zhang, Zhuomin M.
Format: Preprint
Published: 2026
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_version_ 1866912973052706816
author Bohm, Preston
Li, Mingjun
Menon, Akanksha K.
Zhang, Zhuomin M.
author_facet Bohm, Preston
Li, Mingjun
Menon, Akanksha K.
Zhang, Zhuomin M.
contents The photomolecular effect has been hypothesized to enhance evaporation of water at visible wavelengths. This study develops a measurement technique to investigate its presence and magnitude at the liquid-vapor interface of water. The experiment detects surface absorptance by comparing polarized reflectance for substrates with and without a water layer. The reflectance ratio is used as an indicator of interfacial absorptance or attenuation. Lightly doped silicon and platinum were used as dielectric and metal substrates, and their pseudo-optical properties were measured using ellipsometry. Experimental results were compared to a multilayer reflectance model to determine theoretical sensitivity and guide angle selection. Measurements showed close agreement with a classical model assuming zero surface absorptance. The model was then extended to include surface absorptance using a spectral response based on Lorentzian-distributed Feibelman parameters derived from a recent estimate of 0.84% interfacial absorption. Although this model predicted a 1-2% reduction in reflectance near resonant frequencies, no such spectral features were observed experimentally. These results suggest that under ambient conditions, interfacial absorption is well below 1%, indicating that the optical signature of the photomolecular effect is either much weaker than previously reported or strongly dependent on conditions not present in this experiment.
format Preprint
id arxiv_https___arxiv_org_abs_2603_17977
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Interfacial optical absorptance of air-water interfaces
Bohm, Preston
Li, Mingjun
Menon, Akanksha K.
Zhang, Zhuomin M.
Optics
The photomolecular effect has been hypothesized to enhance evaporation of water at visible wavelengths. This study develops a measurement technique to investigate its presence and magnitude at the liquid-vapor interface of water. The experiment detects surface absorptance by comparing polarized reflectance for substrates with and without a water layer. The reflectance ratio is used as an indicator of interfacial absorptance or attenuation. Lightly doped silicon and platinum were used as dielectric and metal substrates, and their pseudo-optical properties were measured using ellipsometry. Experimental results were compared to a multilayer reflectance model to determine theoretical sensitivity and guide angle selection. Measurements showed close agreement with a classical model assuming zero surface absorptance. The model was then extended to include surface absorptance using a spectral response based on Lorentzian-distributed Feibelman parameters derived from a recent estimate of 0.84% interfacial absorption. Although this model predicted a 1-2% reduction in reflectance near resonant frequencies, no such spectral features were observed experimentally. These results suggest that under ambient conditions, interfacial absorption is well below 1%, indicating that the optical signature of the photomolecular effect is either much weaker than previously reported or strongly dependent on conditions not present in this experiment.
title Interfacial optical absorptance of air-water interfaces
topic Optics
url https://arxiv.org/abs/2603.17977