Surface optimization and synergistic quantification method for OTS anti-relaxation coatings

To enhance the anti-relaxation performance of alkali metal vapor cells in quantum sensors, a synergistic optimization and quantitative evaluation strategy for surface parameters of octadecyl-trichlorosilane (OTS) anti-relaxation coatings is proposed. By systematically adjusting solution concentration and reaction time, both the polarization retention angle and the surface polarization retention cross-section are effectively optimized, achieving a maximum retention angle of 135°. A theoretical framework is subsequently established to quantify adsorption energy based on the inherent correlation between these two surface parameters. A correction method for the retention cross-section, developed through a non-uniform wetting model, enables in-situ mapping of the kinetic contribution to adsorption behavior. Through kinetic and thermodynamic parameter extraction, the adsorption energy and Gibbs free energy of the multilayer OTS coatings are determined to be 0.13 eV, which represents a substantial reduction compared to the adsorption energy of bare glass surfaces, previously reported as 2.01 eV. Furthermore, longitudinal relaxation time measurements are carried out inside vapor cells, yielding a maximum collision count of 593, which provides strong evidence of polarization preservation capability. This approach provides both theoretical guidance and an experimental pathway for optimizing coating performance and analyzing adsorption mechanisms, thereby facilitating the development of high-performance alkali metal vapor cell materials for quantum sensing applications.