Attractive force on atoms due to blackbody radiation

TL;DR

This paper demonstrates an attractive force on cesium atoms caused by blackbody radiation, which is significantly stronger than radiation pressure and scales with temperature, challenging previous assumptions about negligible scattering effects.

Contribution

The study reveals a measurable attractive force due to blackbody radiation on atoms, showing it dominates over gravity and radiation pressure at various temperatures.

Findings

Force scales with the fourth power of temperature

Force is in agreement with ac Stark shift predictions

Force exceeds gravity and radiation pressure over a large temperature range

Abstract

Objects at finite temperature emit thermal radiation with an outward energy-momentum flow, which exerts an outward radiation pressure. At room temperature, a cesium atom scatters on average less than one of these blackbody radiation photons every 10^8 years. Thus, it is generally assumed that any scattering force exerted on atoms by such radiation is negligible. However, atoms also interact coherently with the thermal electromagnetic field. In this work, we measure an attractive force induced by blackbody radiation between a cesium atom and a heated, centimeter-sized cylinder which is orders of magnitude stronger than the outward directed radiation pressure. Using atom interferometry, we find that this force scales with the fourth power of the cylinder`s temperature. The force is in good agreement with that predicted from an ac Stark shift gradient of the atomic ground state in the thermal radiation field. This observed force dominates over both gravity and radiation pressure, and does so for a large temperature range.