Reporting on pTP sublimation during evaporation deposition

Noble liquid detectors rely on wavelength shifter materials, such as p-terphenyl (pTP) and Tetraphenyl-butadiene (TPB), which are widely used in neutrino and dark matter experiments. Given their importance, a thorough understanding and characterization of these compounds are essential for optimizing experimental techniques and enhancing detector performance. In this study, we report a novel phenomenon in which commonly used wavelength shifters undergo spontaneous sublimation under high vacuum conditions. We quantify the sublimation rates of pTP and TPB as a function of pressure and temperature, assessing their impact on material growth and physical properties. Additionally, we investigate how variations in film thickness and growth rate influence the sublimation process. These findings provide critical insights into improving the handling and preparation of wavelength shifters during the fabrication of light detectors for these experiments, ensuring their stability and performance in low-background photodetection systems.