mb

millibarn

Areaexact by definition

The millibarn is 10⁻³¹ square metres, one thousandth of a barn. It is the working unit for cross sections that are small by nuclear standards: most charged-particle reactions, photonuclear processes and many neutron capture resonances off resonance land in the millibarn range.

1 mb 1.0000000e-31 m²