A square nanometer (often abbreviated as nm²) is a unit of area in the International System of Units (SI) and is used to describe extremely small areas, especially in the context of nanotechnology and scientific research.
One square nanometer is equal to one billionth of a square meter (1 x 10^-9 m²). In other words, it takes one billion square nanometers to make up one square meter.
To give you a sense of scale, a square nanometer is incredibly tiny. It's often used to describe the size of individual atoms, molecules, or the features on nanoscale devices. Nanotechnology deals with structures and materials on this extremely small scale, where traditional units of area, like square meters or even square millimeters, are impractical.
The electron cross-section, often referred to as the electron scattering cross-section or simply the electron cross-section, is a term used in the fields of nuclear and particle physics to describe the likelihood of electrons interacting with other particles, such as atomic nuclei or other electrons, when they are subjected to various types of scattering experiments or interactions.
The electron cross-section is typically expressed in units of area, such as square meters (m²) or square femtometers (fm²), and it represents the effective target area presented by an electron for a particular type of interaction or scattering process. It is used to quantify the probability of electron interactions occurring in various experimental setups.