Raman and nuclear magnetic resonance investigation of alkali metal vapor interaction with alkene-based anti-relaxation coating

TL;DR

This study uses Raman and NMR techniques to explore how alkali metals interact with alpha-olefin coatings in vapor cells, revealing chemical changes during curing that impact cell performance.

Contribution

It provides the first detailed physicochemical analysis of alkali metal effects on alpha-olefin anti-relaxation coatings during curing.

Findings

Alkali metals catalyze migration of double bonds in the coating.

Curing involves formation of cis- and trans-2-nonadecene.

Chemical changes influence the coating's anti-relaxation properties.

Abstract

The use of anti-relaxation coatings in alkali vapor cells yields substantial performance improvements by reducing the probability of spin relaxation in wall collisions by several orders of magnitude. Some of the most effective anti-relaxation coating materials are alpha-olefins, which (as in the case of more traditional paraffin coatings) must undergo a curing period after cell manufacturing in order to achieve the desired behavior. Until now, however, it has been unclear what physicochemical processes occur during cell curing, and how they may affect relevant cell properties. We present the results of nondestructive Raman-spectroscopy and magnetic-resonance investigations of the influence of alkali metal vapor (Cs or K) on an alpha-olefin, 1-nonadecene coating the inner surface of a glass cell. It was found that during the curing process, the alkali metal catalyzes migration of the carbon-carbon double bond, yielding a mixture of cis- and trans-2-nonadecene.