 [I]- IBA Ion beam analysis.
- ICPMS Inductively coupled plasma mass spectrometry.
- IDA Isotope dilution analysis.
- IDMS Isotope dilution mass spectrometry.
- IMMUNOASSAY An assay procedure based on the reversible and non-covalent binding of an antigen by an antibody. Immunoassays can be employed to detect or quantify either antigens (haptens) or antibodies.
- IMMUNOGEN A substance that induces an immune response, one that stimulates the production of specific antibody or lymphocytes.
- IMMUNORADIOMETRIC ASSAY An assay procedure based on the reversible and non-covalent binding of an antigen by a specific antibody labeled with a radioactive nuclide as tracer. Synonymous with radiometric assay. KE.
- IMMUNORADIOMETRIC ASSAY, TWO-SITE An immunoradiometric assay involving two sets of antibodies, one of which is labeled , that combine with different immunoreactive sites of an antigen molecule.
- INAA Instrumental neutron activation analysis.
- INDEPENDENT FISSION YIELD See fission yield, independent.
- INDICATOR, RADIOACTIVE A radioactive substance which functions as an indicator for various chemical, physicochemical, etc. processes, e.g., absorption, precipitation or extraction.
- INDUCED RADIOACTIVITY Radioactivity induced by irradiation.
 INELASTIC SCATTERING Scattering in which the total kinetic energy of the two collision partners changes.- INFINITE SOURCE THICKNESS For a specified radiation , the minimum thickness of a flat preparation of a radioactive material where the intensity of the specified radiation at the surface does not increase when the thickness is increased by adding more of similar radioactive material.
- INNER BREMSSTRAHLUNG See bremsstrahlung, inner.
- IN SOURCE See isotopic neutron source. KE.
- INSTRUMENTAL ACTIVATION ANALYSIS See activation analysis, instrumental.
- INSTRUMENTAL PHOTON ACTIVATION ANALYSIS Activation analysis in which high-energy photonuclear reactions are used for the activation. KE.
- INTEGRAL FLUX The total particle flux density encompassing all particle energies. KE.
- INTEGRATED FLUX See fluence. KE.
- INTENSITY OF RADIATION The energy per unit time entering a small sphere in a time interval, divided by the area of the great circle of the sphere and the time interval. For mono-directional radiation , this reduces to the energy flux density.
- INTERCOMPARISON, ANALYTICAL A procedure which gives insight into the accuracy of results of analytical procedures by comparing the results obtained in the analyses of identical samples at different laboratories and preferably with different analytical methods.
- INTERFERENCE, NUCLEAR In activation analysis for a particular element producing a radionuclide, the formation of that same radionuclide from another element.
- INTERFERENCE, SPECTRAL An interference caused by 1.) unresolved overlapping with a neighboring spectral peak, 2.) disturbing of proper spectrometer response at a peak due to high levels of background or of other radionuclides.
- INTERNAL CONVERSION See conversion, internal.
- INTERNAL CONVERSION COEFFICIENT See conversion coefficient, internal.
- INTERNAL MONITOR Beam monitoring in which the monitor is part of the target or target assembly being irradiated.
- INTERSTITIAL Pertaining to or situated in the interspaces of a tissue or other structure. NM.
- INTRINSIC EFFICIENCY See detector efficiency.
- INTRINSIC FULL ENERGY PEAK EFFICIENCY See full energy peak efficiency, intrinsic.
- INTRINSIC Ge DETECTORS See Germanium detector, high purity.
- INTRINSIC PHOTOPEAK EFFICIENCY See photopeak efficiency, intrinsic.
- INVERSE SQUARE LAW The intensity of radiation from a point source in free space is inversely proportional to the square of the distance from the source. Presence of absorbers necessitates corrections to this law.
- ION An atomic or molecular particle having a net electric charge.
- ION BEAM A charged-particle beam.
- ION BEAM ANALYSIS A collective term for any of a variety of techniques that involve irradiation of a sample with an ion beam for the purpose of analysis. Included are particle-induced gamma and x-ray emission, Rutherford backscattering spectroscopy, nuclear microprobes and other methods of nuclear reaction analysis.
- (ION CHROMATOGRAPHY)
- ION DENSITY The number of ions per unit volume. Also known as ion concentration. M.
- ION EXCHANGE 1. In surface chemistry, if the adsorption of one or several ionic species is accompanied by the simultaneous desorption (displacement) of an equivalent amount of one or more other ionic species, this process is called ion exchange. 2. The process of exchanging ions between a solution and an ion exchanger. C.
- ION EXCHANGE CHROMATOGRAPHY Separation based mainly on differences in the ion-exchange affinities of the components. C.
- ION EXCHANGER A solid or liquid, inorganic or organic, containing ions exchangeable with others of the same sign present in a solution in which the exchanger is considered to be insoluble. A monofunctional ion exchanger contains only one type of ionogenic group, that is, a group which is either ionized or capable of dissociation into fixed ions and mobile counter-ions. C.
- IONIZATION The formation of ions by addition or removal of electrons from atoms , molecules, or groups of molecules or by the division of molecules.
- IONIZATION CHAMBER A radiation detector which employs an electric field for the collection at the electrodes of charges associated with the ions produced in the sensitive volume by ionizing radiation , without charge multiplication. The solid angle (2, 4) subtended when using the detector is sometimes specified.
- IONIZATION CURRENT The passage of a charged particle through a gas causes ionization; if an electric field is applied across the gas a current (due to the motion of the ions produced) flows between the electrodes. NM.
- IONIZATION DENSITY The density of the ionization, produced in the path of a charged particle passing through matter, depends upon the amount of charge, the velocity of the particle, and the nature of the matter. NM.
- IONIZATION ENERGY The minimum energy required to ionize an atom or molecule which is originally in the ground state.
- IONIZATION POTENTIAL See ionization energy.
- IONIZING RADIATION Any radiation consisting of directly or indirectly ionizing particles or a mixture of both or photons with energy higher than the energy of photons of ultraviolet light or a mixture of both such particles and photons.
- IONIZATION, SPECIFIC See specific ionization.
- ION MICROPROBE The probe used in ion probe microanalysis.
- ION PAIR A pair of oppositely charged ions, or an electron and a cation, held together by Coulombic attraction without formation of a covalent bond.
- ION GEMINATE PAIRS Ion pairs in which oppositely charged particles are held together at certain equilibrium distance by Coulomb attraction.
- ION PROBE MICROANALYSIS Any technique in which the specimen is bombarded by a focused beam of (primary) ions (diameter less than 10 mm) and the (secondary) ions ejected from the specimen are detected after passage through a mass spectrometer. C.
- IPAA See instrumental photon activation analysis.
- IPAC Integral perturbed angular correlation.
- IPMA Ion probe microanalysis.
- IRIDIUM ANOMALY The name given to the sharp maximum observed in iridium abundance versus depth profile of certain geologic formations. Discovered in 1979, the interpretation remains controversial.
- IRMA See immunoradiometric assay.
- IRMS Isotope ratio mass spectrometer.
- IRRADIATION Exposure to ionizing radiation.
- ISOBARS, NUCLEAR Nuclides having the same mass number but different atomic numbers.
- ISODIAPHERES Nuclei having equal neutron excesses.
- ISOMER One of two or more nuclides having the same mass number A and atomic number Z, but existing for measurable times in different nuclear energy states.
- ISOMERIC STATE An excited nuclear state having a mean life long enough to be observed.
- ISOMERIC TRANSITION A spontaneous transition between two isomeric states of a nucleus or between an isomeric state and the ground state of a nucleus.
- ISOMERS, NUCLEAR See isomer.
- ISORAD In nuclear geology , contours of equal radioactivity.
- ISOSPIN In nuclear structure, a quantum mechanical formalism in which the charge on a nucleon is treated like the spin of an electron, that is, half-integral with two possible orientations. The 0 and +1 charges become +(1/2) and -(1/2) isospins. FKMM.
- ISOTONES Nuclides having the same neutron number but different atomic numbers.
- ISOTOPES Nuclides having the same atomic number but different mass numbers.
- ISOTOPE DILUTION Mixing of a given nuclide with one or more of its isotopes.
- ISOTOPE DILUTION ANALYSIS A method of quantitative analysis based on the measurement of the isotopic abundance of a nuclide after dilution by mixing with one or more of its isotopes.
- ISOTOPE DILUTION ANALYSIS, DIRECT Isotope dilution analysis used for the determination of a non-radioactive element with the aid of one of its radionuclides.
- ISOTOPE DILUTION ANALYSIS, REVERSED Isotope dilution analysis used for the determination of the isotopic carrier in a solution of a radionuclide with the aid of one of its stable isotopes.
- ISOTOPE DILUTION ANALYSIS, SUBSTOICHIOMETRIC A method of isotope dilution analysis. The final isotopic abundance is estimated from the amount of the nuclide present in a quantity of the relevant element separated from the sample. That quantity must be identical to the quantity isolated from a standard solution of the radioisotope added. The analysis requires that the separations be substoichiometric, adding identical but smaller than stoichiometric amounts of the reagent to the standard and diluted sample solutions.
- ISOTOPE EFFECT The difference in behavior between two substances of which only the mass numbers of one or more of the constituent atoms are different.
- ISOTOPE EXCHANGE Any process which does not lead to usual physicochemical changes of the system, but changes the distribution of the isotopes of the given element between different chemical forms, different phases, or inside molecules. (Roginskij, S. Z.: Theoretische Grundlagen der Isotopenchemie. VEB-Deutscher Verlag der Wissenschaften, Berlin 1962.) The exchange of places between isotopes of atoms in different valency states, in different molecules or ions, or in different sites in the molecule or ion.
- ISOTOPE EXCHANGE ANALYSIS A method of quantitative analysis based on the isotope exchange between isotopes of the element to be determined and other isotopes of this element in different valency state or in different molecules.
- ISOTOPE FARM A closed biological growth chamber in which biochemically labeled compounds are produced by growth in an isotopically enriched nutrient environment.
- ISOTOPE, STABLE A nuclide which is not radioactive.
- ISOTOPE GEOCHRONOLOGY Determining the age of geological materials using radiochemical or other isotopic dating techniques.
- ISOTOPE GEOLOGY Investigation of geological phenomena by means of stable and radioactive isotopes of elements and of changes in their abundance.
- ISOTOPE HYDROLOGY The study of the properties and distribution of water on the surface of the earth, in the soil and rocks, and in the atmosphere as measured using stable and radioactive isotopes and measurements of their abundances.
- ISOTOPE RATIO MASS SPECTROMETRY A mass spectroscopic instrument with low resolution but excellent precision able to determine very small changes in the isotopic composition of gas samples. J.
- ISOTOPIC ABUNDANCE See abundance, isotopic.
- ISOTOPIC CARRIER See carrier, isotopic.
- ISOTOPIC MODIFICATION Preparing a compound that has a macroscopic composition such that the isotopic ratio of nuclides for at least one element deviates measurably from that occurring in nature.
- ISOTOPIC NEUTRON SOURCE Neutron sources generated by a spontaneously fissioning nuclide or by a nuclear reaction induced by radiation from one radioisotope in a mixture.
- ISOTOPIC NUCLIDES Isotopes.
- ISOTOPIC SEPARATION Operation for the purpose of modifying an isotopic abundance in a mixture of isotopes.
- ISOTOPIC SUBSTITUTION A process in which all molecules have a specified nuclide at a specified position. KE.
- ISOTOPIC TRACER See tracer, isotopic.
- ISOTOPOMER Chemically identical structures that differ in the atomic mass of one or more of their elements. J.
- ISOTRON A device for sorting isotopes of an element in which ions are accelerated to a fixed energy in a strong electric field and an radiofrequency field then selects ions according to their velocity which is inversely proportional to the square root of their mass. M.
- IT Isomeric transition.
- IVNAA In vivo neutron activation analysis.
- IVPGAA In vivo prompt gamma neutron activation analysis. CRC.
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