Investigation of Anti-Relaxation Coatings for Alkali-Metal Vapor Cells Using Surface Science Techniques

TL;DR

This study uses advanced surface science techniques to analyze paraffin coatings in alkali-metal vapor cells, aiming to understand their properties that preserve atomic spin polarization and improve coating performance.

Contribution

The paper applies modern surface and bulk analysis methods to characterize paraffin coatings, revealing key properties like crystallinity independence and presence of C=C bonds that influence their effectiveness.

Findings

Crystallinity of paraffin coatings is not necessary for effectiveness.

Presence of C=C double bonds correlates with coating performance.

Different paraffin materials show varying light-induced atomic desorption yields.

Abstract

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of anti-relaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10,000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings, in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge X-ray absorption fine structure spectroscopy, and X-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C=C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin anti-relaxation coatings, as well as the design and synthesis of new classes of coating materials.