Quantum Suppression of Alignment in Ultrasmall Grains: Microwave Emission from Spinning Dust will be Negligibly Polarized

TL;DR

This paper demonstrates that quantum effects in ultrasmall dust grains significantly suppress their alignment and polarization, implying that microwave emission from spinning dust is nearly unpolarized at GHz frequencies.

Contribution

It introduces a quantum mechanical model showing suppression of grain alignment and polarization in ultrasmall grains, impacting interpretations of microwave emission observations.

Findings

Polarization of spinning dust emission is negligible at GHz frequencies.

Quantum suppression of dissipation reduces grain alignment.

Implications for polarization measurements in cosmic microwave background studies.

Abstract

The quantization of energy levels in very nanoparticles suppresses dissipative processes that convert grain rotational kinetic energy into heat. For grains small enough to have GHz rotation rates, the suppression of dissipation can be extreme. As a result, alignment of such grains is suppressed. This applies both to alignment of the grain body with its angular momentum J, and to alignment of J with the local magnetic field B_0. If the anomalous microwave emission is rotational emission from spinning grains, it will be negligibly polarized at GHz frequencies, with P < 10^{-6} at frequencies above 10 GHz.