Alpha Decay (A) : In alpha decay, the nucleus of an atom of atomic number Z and mass number A emits an alpha particle (⁴He nucleus) to form an atom of atomic number Z - 2 and mass number A - 4.

Background Radiation: Background radiation is constantly present in the environment and is emitted from a variety of natural and artificial sources. The user should account for and add the background radiation to the Goal Detector Response.

Beta-minus Decay (B-) : In beta-minus decay, the nucleus of an atom of atomic number Z and mass number A emits a negative electron (B-) and an antineutrino to form an atom of atomic number Z + 1 and mass number A.

Beta-plus Decay (B+) : In beta-plus decay, the nucleus of an atom of atomic number Z and mass number A emits a positive electron (B+) and an antineutrino to form an atom of atomic number Z - 1 and mass number A.

Bequerel (Bq) : The SI derived unit of radioactivity. One Becquerel is defined as one decay per second.

Counts per Minute (cpm) : The number of counts a radiation detector records in a minute.

Curie (Ci) : A unit of radioactivity defined as 3.7x10¹⁰ Becquerels.

Decay Mode : The method of radioactive decay.

Detector Efficiency : A measure of the detector's ability to see and record an incident particle; between 0 and 1.

Disintegrations per Minute (dpm) : A measure of radioactivity; 1 Bq = 60 dpm.

Electron Capture Decay (EC): In electorn capture decay, the nucleus of an atom of atomic number Z and mass number A captures an atomic electron and emits a neutrino to form an atom of atomic number Z - 1 and mass number A.

Gamma Attenuation: The loss of radiation intensity due to the geometry of the source-detector system and the attenuation of particles in air.

Gamma Ray: An electromagnetic radiation, also called photons, that are emitted by the nucleus in transition from a high energy state to a low energy state.

Goal Detector Response: The acceptable detector response for the safe measure of activity in soil in counts per minute (cpm).

Half-life (T_1/2): The interval required for a radionuclide's activity to decay to half of its initial value.

Internal Conversion (IC): A radioactive decay process where the gamma ray emitted from a nucleus is photoelectrically absorbed by one of the most tightly bound electrons causing it to be ejected from the atom. After the ejection of the internal conversion electron the vacancy is filled by another shell electron with a corresponding emission of one or several x-rays or Auger electrons.

Isomeric Transition Decay (IT): A nucleus in an excited energy state of an atom of atomic number Z and mass number A can transition to a lower energy state by emission of a gamma ray, or eject an orbital electron with the excess energy. No change in atomic number and mass numbers occurs; the parent and daughter nuclei are isomers.

Nuclide: An atom with the same atomic number (number of protons) but with more or less neutrons which often contributes to the stability (radioactivity) of the atom.

PicoCurie (pCi): A unit of radioactivity defined as 1x10^-12 Curies.

Principal Photon: The emitted photon with the highest yield.

Principal Photon Energy: The energy of the principal photon emitted from the nuclide.

Principal Photon Yield (Y%): A measure of the number of principal photons emitted per decay of a nuclide. This number may be greater than 1 due to the emittance of multiple photons of the principal energy, or less than 1 if thme emittance is a statistically random occurrence.

Principal Photon Yield (Y%): A measure of the number of principal photons emitted per decay of a nuclide. This number may be greater than 1 due to the emittance of multiple photons of the principal energy, or less than 1 if the emittance is a statistically random occurrence.

Remedial Goal: The safe level of remedial activity.

Spontaneous Fission (SF): A decay mechanism resulting in splitting of the nucleus into lighter nuclei, referred to as 'fission fragments', with the emission of neutrons and release of energy.