Radiation of microwaves and infrared by slender graphite needles

Abstract

It has become clear from sources observed by IRAS that there are many examples which attain maximum emission per unit (frequency) bandwidth longward of 100 μm. Here, we show that a large emissivity at such long wavelengths can be obtained by needle-shaped particles of free carbon. Indeed for needles with a sufficiently high ratio of length to diameter the large emissivity extends from the infrared through the whole microwave region of the spectrum.