I

I

atomic symbol for iodine

ICP-MS, or ICP/MS

1. inductively coupled plasma mass spectrometry
2. inductively coupled plasma mass spectrometer

immobile phase

stationary phase

In

atomic symbol for indium

in control

in a state of statistical control (cf. out of control)

independent

A collection of random variables, X₁,X₂,…,X_N, is independent if for any real numbers x₁,x₂,…,x_N,

Pr(X₁ ≤ x₁, X₂ ≤ x₂, …, X_N ≤ x_N) = Pr(X₁ ≤ x₁) · Pr(X₂ ≤ x₂) ⋯ Pr(X_N ≤ x_N).

indication (of a measuring instrument)

“value of a quantity provided by a measuring instrument” [VIM]

influence quantity

in a measurement process, any quantity that is not the measurand but which influences the result of the measurement, such as air temperature and humidity during a mass meas­ure­ment using a balance

ingrowth

increase in the amount of a nuclide due to the decay of one or more of its ancestors

ingrowth factor

amount of a nuclide expected to be present because of ingrowth from an ancestor, divided by the amount of the ancestor initially present

Note: The value of the ingrowth factor depends on whether the amounts are expressed as activities or numbers of atoms.

input estimate

estimated value of an input quantity in a mathematical model of measurement

input quantity

in a mathematical model of measurement, any of the particular quantities whose values are either measured or imported, and used in the calculation of a value for the output quantity, which is also the measurand

When the measurement function is written abstractly as Y = f(X₁,X₂,…,X_N), the input quantities are X₁,X₂,…,X_N and the output quantity is Y.

Note: An estimated value x_i for an input quantity X_i is called an input estimate.

in situ measurement

measurement made in place in the field without collecting a sample for laboratory analysis

intensity

1. rate of radiant energy flux, equal to the product of the energy density and the velocity of the radiation
2. probability of emission of a given radiation during the decay of an atom of a given radionuclide; radiation emission probability — also called abundance

internal conversion

mode of radioactive decay in which an excited nucleus imparts its excitation energy to an orbital electron, which is thereupon ejected from the atom

The ejected electron is called a conversion electron.

International System of Units (SI)

the coherent system of units recommended by the General Conference on Weights and Measures (CGPM), which currently has the following base units:

• meter (length)
• second (time)
• kilogram (mass)
• ampere (electric current)
• kelvin (thermodynamic temperature)
• mole (amount of substance)
• candela (luminous intensity)

ion

atom or molecule that has gained or lost elec­trons and thereby acquired a net nega­tive or posi­tive charge (see also anion and cation)

ion-exchange chromatography

chromatographic separation based on the reversible exchange of ions in a mobile phase with ions in a solid stationary phase

ionization

production of ions in matter, as for example by ionizing radiation

ionization chamber

device that detects radiation by collecting ion pairs produced when incident radiation ionizes gas in a chamber

A voltage is applied to electrodes in the chamber, causing the ion pairs to migrate to the elec­trodes, where they may pro­duce either pulses or a steady cur­rent, de­pend­ing on the mode of operation.

ionization current

electrical current produced in an ion chamber when incident radiation ionizes gas in the chamber and the result­ing ion pairs migrate toward the chamber’s electrodes

ionizing radiation

radiation that can cause ionization, either directly or indirectly, when it passes through matter

ion pair

The positive ion and free electron produced when radiation ionizes a neutral atom. The free elec­tron may sub­sequently com­bine with a neutral atom to form a nega­tive ion, in which case the posi­tive ion and nega­tive ion also form an ion pair. 

Ir

atomic symbol for iridium

ISO

International Organization for Standardization.

isomeric state

nuclear energy state having a mean life­time long enough to be observable

isomers

compounds whose molecules have the same numbers and types of atoms but different structural arrangements and somewhat different chemical properties (see also nuclear isomers)

isomeric transition (IT)

mode of nuclear decay in which a radionuclide makes a spontaneous transition to a different isomeric state, either by gamma-ray emission or internal conversion

isotopes

nuclides having the same atomic number but different mass numbers [IUPAC]

isotopic abundance

relative number of atoms of a particular isotope in a mixture of the isotopes of the element, expressed as a fraction of all the atoms of the element [IUPAC]

Note: The term is often used to denote the natural isotopic abundance, or the relative abundance of an isotope as it is found naturally on the Earth.

isotope dilution

mixing of a given nuclide with one or more of its isotopes [IUPAC]

isotope dilution analysis

kind of quantitative analysis based on the measurement of the isotopic abundance of a nuclide after isotope dilution with the test portion [IUPAC]

isotopic enrichment

any process that increases the isotopic abundance of a particular isotope of an element

IUPAC

International Union of Pure and Applied Chemistry.