High-Temperature Alkali Vapor Cells with Anti-Relaxation Surface Coatings

TL;DR

This paper demonstrates that octadecyltrichlorosilane (OTS) coatings enable high-temperature alkali vapor cells with long spin relaxation times, improving atomic magnetometer sensitivity and linewidth at temperatures up to 170°C.

Contribution

It introduces OTS as an effective high-temperature antirelaxation coating for alkali vapor cells, expanding operational temperature range beyond 80°C.

Findings

OTS coating remains effective up to 170°C for potassium and rubidium.

Achieved a magnetometer sensitivity of 6 fT/√Hz.

Narrow magnetic linewidth of 2 Hz at high temperature.

Abstract

Antirelaxation surface coatings allow long spin relaxation times in alkali-metal cells without buffer gas, enabling faster diffusion of the alkali atoms throughout the cell and giving larger signals due to narrower optical linewidths. Effective coatings were previously unavailable for operation at temperatures above 80 C. We demonstrate that octadecyltrichlorosilane (OTS) can allow potassium or rubidium atoms to experience hundreds of collisions with the cell surface before depolarizing, and that an OTS coating remains effective up to about 170 C for both potassium and rubidium. We consider the experimental concerns of operating without buffer gas and with minimal quenching gas at high vapor density, studying the stricter need for effective quenching of excited atoms and deriving the optical rotation signal shape for atoms with resolved hyperfine structure in the spin-temperature regime. As an example of a high-temperature application of antirelaxation coated alkali vapor cells, we operate a spin-exchange relaxation-free atomic magnetometer with sensitivity of 6 fT/sqrt(Hz) and magnetic linewidth as narrow as 2 Hz.