Electric-field-induced change of alkali-metal vapor density in paraffin-coated cells

TL;DR

Applying an electric field to paraffin-coated alkali vapor cells causes a rapid increase, followed by a decrease, and then a slow recovery in vapor density, indicating a field-induced modification of the coating affecting vapor behavior.

Contribution

This study reveals a novel electric-field-induced change in alkali vapor density in paraffin-coated cells, providing new insights into coating behavior under electric fields.

Findings

Rapid vapor density increase (< 100 ms) upon electric field application

Subsequent decrease (~ 1 s) below equilibrium vapor density

Slow recovery (~ 100 s) to equilibrium vapor density

Abstract

Alkali vapor cells with antirelaxation coating (especially paraffin-coated cells) have been a central tool in optical pumping and atomic spectroscopy experiments for 50 years. We have discovered a dramatic change of the alkali vapor density in a paraffin-coated cell upon application of an electric field to the cell. A systematic experimental characterization of the phenomenon is carried out for electric fields ranging in strength from 0-8 kV/cm for paraffin-coated cells containing rubidium and cells containing cesium. The typical response of the vapor density to a rapid (duration < 100 ms) change in electric field of sufficient magnitude includes (a) a rapid (duration of < 100 ms) and significant increase in alkali vapor density followed by (b) a less rapid (duration of ~ 1 s) and significant decrease in vapor density (below the equilibrium vapor density), and then (c) a slow (duration of ~ 100 s) recovery of the vapor density to its equilibrium value. Measurements conducted after the alkali vapor density has returned to its equilibrium value indicate minimal change (at the level of < 10%) in the relaxation rate of atomic polarization. Experiments suggest that the phenomenon is related to an electric-field-induced modification of the paraffin coating.