(DGNAA), see Neutron Activation Analysis.

Henri Becquerel demonstrated beta particles in 1900. Identical with electrons is there negative charge at -1. Their mass is 549 millionths of one AMU, 1/2000 of the mass of a proton or neutron. Beta particles consist of high energetic electrons emitted by radioactive nuclei or neutrons. By the process of beta decay, one of the neutrons in the nucleus is transformed into a proton and a new atom is formed which has one less neutron but one more proton in the core. Beta decay is accompanied by the emission of a positron (the antiparticle of the electron), a positive charged antineutrino. Beta particles have a greater range of penetration than alpha particles but less than gamma rays or x-rays. The name beta was coined by Rutherford in 1897. The traveling speed of beta particles depends on their energy. Because of their small mass and charge beta particles travel deep into tissues and cause cellular damage and possible cancer.

See also Radiation Shielding.

Activation is the production of radionuclides (instable atoms) by bombarding atomic nuclei (stable atoms) with radiation (e.g., photons, neutrons, alpha particles).
With the activation of an atom its decay starts.

See Neutron Activation, Neutron Activation Analysis.

Concentration determination of trace elements, halogens, lead, arsenic and mercury in pharmaceuticals by neutron activation.

See Neutron Activation Analysis.

Alpha particles consist of two neutrons and two protons (nucleus of He), have a positive charge of 2 and a velocity in air of approximately one-twentieth the speed of light.
Discovered by Ernest Rutherford in 1899 (Rutherford-Bohr planetary atom model) alpha particles became emitted by very large atoms in an unstable energy state (high atomic number mostly over 82, with a too low neutrons//protons ratio (e.g. <= 1.5)).
Through their relative slow travel speed, they get stopped by e.g. a thin sheet of paper or the outer layers of human skin or travel only inches; once stopped they pick up free electrons and become helium.
These alpha particles are only dangerous to humans when the alpha-emitting material is inhaled or ingested (it causes damage that may lead to cancer) or comes into contact with the lens of the eye, caused by their less penetrating properties.