Isotope Mass Spectrometry
Encyclopedia
Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry
, in which mass spectrometric methods are used to measure the relative abundance of isotope
s in a given sample.
methods.
Most instruments used for precise determination of isotope ratios are of the magnetic sector
type. This type of analyzer is superior to the quadrupole type in this field of research for two reasons. First, it can be set up for multiple-collector analysis, and second, it gives high-quality 'peak shapes'. Both of these considerations are important for isotope-ratio analysis at very high precision and accuracy.
The sector-type instrument designed by Alfred Nier was such an advance in mass spectrometer design that this type of instrument is often called the 'Nier type'. In the most general terms the instrument operates by ionizing the sample of interest, accelerating it over a potential in the kilo-volt range, and separating the resulting stream of ions according to their mass-to-charge ratio (m/z). Beams with lighter ions bend at a smaller radius than beams with heavier ions. The current of each ion beam is then measured using a 'Faraday' detector or multiplier detector.
Many radiogenic isotope measurements are made by ionization of a solid source, whereas stable isotope measurements of light elements (e.g. H, C, O) are usually made in an instrument with a gas source. In the latter case, dual gas inlets enable reliable repetition of measurements by supplying continuous streams of the reference and sample gases, which are sequentially switched by a changeover valve. The IRMS's collector also features an array of Faraday cups (conductive, metal vessels which neutralise ions that hit them whilst themselves becoming charged), or "multicollector", which allows the simultaneous detection of multiple isotopes. Samples must be introduced as pure gases, achieved through combustion, gas chromatographic feeds, or chemical trapping. By comparing the detected isotopic ratios to a measured standard, an accurate determination of the isotopic make up of the sample is obtained. For example, carbon isotope ratios are measured relative to the international standard for CO2. (The CO2 standard is produced from a fossil belemnite found in the Pee Dee
formation, which is a limestone formed in the Cretaceous period in South Carolina
, U.S.A.; its 13C:12C ratio is 0.0112372.) Oxygen isotope ratios are measured relative the standard, V-SMOW (Vienna Standard Mean Ocean Water).
66.
This field is of interest because the relative variation in mass between isotopes in this range is large enough to give rise to variation in chemical, physical and biological behaviour. This leads to measurable effects on the isotopic composition of samples characteristic of their biological or physical history.
As a specific example, the hydrogen
isotope deuterium
(heavy hydrogen) is almost double the mass of the common hydrogen isotope. Water molecules containing the common hydrogen isotope (and the common oxygen isotope, mass 16) have a mass of 18. Water incorporating a deuterium atom has a mass of 19, over 5% heavier. The energy to vaporise the heavy water molecule is higher than that to vaporize the normal water so isotope fractionation occurs during the process of evaporation.
Thus a sample of sea water (Vienna Standard Mean Ocean Water, or VSMOW) will exhibit a quite detectable isotopic-ratio difference when compared to Arctic snowfall (standard light Arctic precipitation, or SLAP).
It is critical that the sample be processed before entering the mass spectrometer so that only a single chemical species enters at a given time. Generally, samples are combusted or pyrolyzed and the desired species (usually hydrogen gas H2, nitrogen (N2), carbon dioxide, or sulfur dioxide) is purified by means of traps, filters, catalysts and/or chromatography.
The two most common types of IRMS instruments are continuous flow and dual inlet. In dual inlet IRMS, purified gas obtained from a sample is alternated rapidly with a standard gas (of known isotopic composition) by means of a system of valves, so that a number of comparison measurements are made of both gases. In continuous flow IRMS, sample preparation occurs immediately before introduction to the IRMS, and the purified gas produced from the sample is measured just once. The standard gas may be measured before and after the sample or after a series of sample measurements. While continuous-flow IRMS instruments can achieve higher sample throughput and are more convenient to use than dual inlet instruments, the yielded data is of approximately 10-fold lower precision.
or isotope geochemistry
. Important examples are argon-argon dating
and helium isotope analysis.
depend on IRMS using thermal ionization
of a solid sample loaded into the source of the mass spectrometer (hence thermal ionization mass spectrometry, TIMS
). These methods include rubidium-strontium dating
, uranium-lead dating
, lead-lead dating
and samarium-neodymium dating
.
When these isotope ratios are measured by TIMS, mass-dependent fractionation occurs as species are emitted by the hot filament. Fractionation occurs due to the excitation of the sample and therefore must be corrected for accurate measurement of the isotope ratio.
There are several advantages of the TIMS method. It has a simple design, is less expensive than other mass spectrometers, and produces stable ion emissions. It requires a stable power supply, and is suitable for species with a low ionization potential, such as Strontium
(Sr), and Lead
(Pb).
The disadvantages of this method stem from the maximum temperature achieved in thermal ionization. The hot filament reaches a temperature of less than 2500 degrees Celsius, leading to the inability to create atomic ions of species with a high ionization potential, such as Osmium
(Os), and Tungsten
(Hf-W). Although the TIMS method can create molecular ions instead in this case, species with high ionization potential can be analyzed more effectively with MC-ICP-MS.
analysis uses a quadrupole analyser, which only allows single-collector analysis. Due to the inherent instability of the plasma, this limits the precision of ICP-MS with a quadrupole analyzer to around 1%, which is insufficient for most radiogenic isotope systems.
Isotope-ratio analysis for radiometric dating
has normally been determined by TIMS. However, some systems (e.g. Hf-W and Lu-Hf) are difficult or impossible to analyse by TIMS, due to the high ionization potential of the elements involved. Therefore these methods can now be analysed using MC-ICP-MS.
Magnetic sector mass spectrometry requires a high acceleration potential in order to properly resolve species with different masses. Since the ion beam is normally positive, a multi-collector ICP-MS (unlike conventional ICP-MS) needs to have an ion source up to 8000 V positive, in order to keep the analyzer at electrical ground. This was one of the engineering challenges of developing MC-ICP-MS. Magnetic sector mass spectrometry also requires an ion beam with a relatively small range in ion energy. This is achieved in MC-ICP-MS by using an electrostatic and/or quadrupole pre-filter, which allows the ion energy of the beam to be homogenized before entering the magnetic sector.
ratios of compounds in a solution, such as after purification by liquid chromatography. The solution (or outflow from the chromatography) is dried onto a nickel or stainless steel wire. After the residue is deposited on the wire, it enters a furnace where the sample is converted to CO2 and water by combustion. The gas stream finally enters a capillary, is dried, ionized, and analyzed. This process allows a mixture of compounds to be purified and analyzed continuously, which can decrease the analysis time by a factor of four. Moving wire IRMS is quite sensitive, and samples containing as little as 1 nano-mole
of Carbon can yield precise (within 1‰) results.
(AMS) can be used. For example, the decay rate of the radioisotope 14C is widely used to date organic materials, but this approach is limited to relatively large samples no more than a few thousand years old. AMS extended the range of 14C dating to about 60,000 years BP, and is about 106 times more sensitive than conventional IRMS.
since most samples will lie between these two extremes. Given a sample of water from an aquifer
, and a sufficiently sensitive tool to measure the variation in the isotopic ratio of hydrogen in the sample, it is possible to infer the source, be it ocean water seeping into the aquifer or precipitation seeping into the aquifer, and even to estimate the proportions from each source.
Another application is in paleotemperature measurement for Paleoclimatology
. For example one technique is based on the variation in isotopic fractionation of oxygen by biological systems with temperature.
Species of foraminifera
incorporate oxygen as calcium carbonate in their shells. The ratio of the oxygen isotopes oxygen 16 and oxygen 18 incorporated into the calcium carbonate varies with temperature and the oxygen isotopic composition of the water. This oxygen remains "fixed" in the calcium carbonate when the forminifera dies, falls to the sea bed, and its shell becomes part of the sediment. It is possible to select standard species of forminifera from sections through the sediment column, and by mapping the variation in oxygen isotopic ratio, deduce the temperature that the forminifera encountered during life if changes in the oxygen isotopic composition of the water can be constrained.
In forensic science, research suggests that the variation in certain isotope ratios in drugs derived from plant sources (cannabis, cocaine) can be used to determine the drug's continent of origin.
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
, in which mass spectrometric methods are used to measure the relative abundance of isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s in a given sample.
Introduction
The isotope-ratio mass spectrometer (IRMS) allows the precise measurement of mixtures of stable isotopes. This technique has two different applications in the earth and environmental sciences. The analysis of 'stable isotopes' is normally concerned with measuring isotopic variations arising from mass-dependent isotopic fractionation in natural systems. On the other hand, radiogenic isotope analysis involves measuring the abundances of decay-products of natural radioactivity, and is used in most long-lived radiometric datingRadiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
methods.
Most instruments used for precise determination of isotope ratios are of the magnetic sector
Sector instrument
A sector instrument is a general term for a class of mass spectrometer that uses a static electric or magnetic sector or some combination of the two as a mass analyzer. A popular combination of these sectors has been the BEB...
type. This type of analyzer is superior to the quadrupole type in this field of research for two reasons. First, it can be set up for multiple-collector analysis, and second, it gives high-quality 'peak shapes'. Both of these considerations are important for isotope-ratio analysis at very high precision and accuracy.
The sector-type instrument designed by Alfred Nier was such an advance in mass spectrometer design that this type of instrument is often called the 'Nier type'. In the most general terms the instrument operates by ionizing the sample of interest, accelerating it over a potential in the kilo-volt range, and separating the resulting stream of ions according to their mass-to-charge ratio (m/z). Beams with lighter ions bend at a smaller radius than beams with heavier ions. The current of each ion beam is then measured using a 'Faraday' detector or multiplier detector.
Many radiogenic isotope measurements are made by ionization of a solid source, whereas stable isotope measurements of light elements (e.g. H, C, O) are usually made in an instrument with a gas source. In the latter case, dual gas inlets enable reliable repetition of measurements by supplying continuous streams of the reference and sample gases, which are sequentially switched by a changeover valve. The IRMS's collector also features an array of Faraday cups (conductive, metal vessels which neutralise ions that hit them whilst themselves becoming charged), or "multicollector", which allows the simultaneous detection of multiple isotopes. Samples must be introduced as pure gases, achieved through combustion, gas chromatographic feeds, or chemical trapping. By comparing the detected isotopic ratios to a measured standard, an accurate determination of the isotopic make up of the sample is obtained. For example, carbon isotope ratios are measured relative to the international standard for CO2. (The CO2 standard is produced from a fossil belemnite found in the Pee Dee
Pee Dee
The Pee Dee region of South Carolina is the northeastern corner of the state. It is the area of the lower watershed of the Pee Dee River, named after the Pee Dee Native American tribe. Its center is Florence...
formation, which is a limestone formed in the Cretaceous period in South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, U.S.A.; its 13C:12C ratio is 0.0112372.) Oxygen isotope ratios are measured relative the standard, V-SMOW (Vienna Standard Mean Ocean Water).
Gas Source ('stable isotope') mass spectrometry
Instruments have been developed based on several techniques for mass separation and tuned to a wide range of applications. The article below describes one of these application areas, instruments adapted specifically to measure the relative abundance of masses up to around mass numberAtomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
66.
This field is of interest because the relative variation in mass between isotopes in this range is large enough to give rise to variation in chemical, physical and biological behaviour. This leads to measurable effects on the isotopic composition of samples characteristic of their biological or physical history.
As a specific example, the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
isotope deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
(heavy hydrogen) is almost double the mass of the common hydrogen isotope. Water molecules containing the common hydrogen isotope (and the common oxygen isotope, mass 16) have a mass of 18. Water incorporating a deuterium atom has a mass of 19, over 5% heavier. The energy to vaporise the heavy water molecule is higher than that to vaporize the normal water so isotope fractionation occurs during the process of evaporation.
Thus a sample of sea water (Vienna Standard Mean Ocean Water, or VSMOW) will exhibit a quite detectable isotopic-ratio difference when compared to Arctic snowfall (standard light Arctic precipitation, or SLAP).
The two most common types of IRMS instruments are continuous flow and dual inlet. In dual inlet IRMS, purified gas obtained from a sample is alternated rapidly with a standard gas (of known isotopic composition) by means of a system of valves, so that a number of comparison measurements are made of both gases. In continuous flow IRMS, sample preparation occurs immediately before introduction to the IRMS, and the purified gas produced from the sample is measured just once. The standard gas may be measured before and after the sample or after a series of sample measurements. While continuous-flow IRMS instruments can achieve higher sample throughput and are more convenient to use than dual inlet instruments, the yielded data is of approximately 10-fold lower precision.
Static Gas ('noble gas') mass spectrometry
A static gas mass spectrometer is one in which a gaseous sample for analysis is fed into the source of the instrument and then left in the source without further supply or pumping throughout the analysis. This method can be used for 'stable isotope' analysis of light gases (as above), but it is particularly used in the isotopic analysis of noble gases (= rare or inert gases) for radiometric datingRadiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
or isotope geochemistry
Isotope geochemistry
Isotope geochemistry is an aspect of geology based upon study of the relative and absolute concentrations of the elements and their isotopes in the Earth. Variations in the abundance of these isotopes, typically measured with an isotope ratio mass spectrometer or an accelerator mass spectrometer,...
. Important examples are argon-argon dating
Argon-argon dating
Argon-argon dating is a radiometric dating method invented to supersede potassium-argon dating in accuracy. The older method required two samples for dating while the newer method requires only one...
and helium isotope analysis.
Solid Source ('radiogenic isotope') mass spectrometry
Several of the isotope systems involved in radiometric datingRadiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
depend on IRMS using thermal ionization
Thermal ionization
In thermal ionization, also referred to as surface ionization, chemically-purified material loaded onto a filament which is then heated to cause some of the material to be ionized as it boils off the hot filament...
of a solid sample loaded into the source of the mass spectrometer (hence thermal ionization mass spectrometry, TIMS
TIMS
TIMS is a four-letter combination that may refer to:* The International Molinological Society* Thermal ionization mass spectrometry - see Thermal ionization* Thermal infrared multispectral scanner - see Thermal infrared spectroscopy and 1982 in archaeology...
). These methods include rubidium-strontium dating
Rubidium-strontium dating
The rubidium-strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks.Development of this process was aided by Fritz Strassmann, who later went on to discover nuclear fission with Otto Hahn and Lise Meitner....
, uranium-lead dating
Uranium-lead dating
Uranium-lead is one of the oldest and most refined of the radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1-1 percent range...
, lead-lead dating
Lead-lead dating
Lead-lead dating is a method for dating geological samples, normally based on 'whole-rock' samples of material such as granite. For most dating requirements it has been superseded by uranium-lead dating , but in certain specialized situations it is more important than U-Pb dating.-Decay equations...
and samarium-neodymium dating
Samarium-neodymium dating
Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites, based on decay of a long-lived samarium isotope to a radiogenic neodymium isotope. Nd isotope ratios are used to provide information on the source of igneous melts as well as to provide age data...
.
When these isotope ratios are measured by TIMS, mass-dependent fractionation occurs as species are emitted by the hot filament. Fractionation occurs due to the excitation of the sample and therefore must be corrected for accurate measurement of the isotope ratio.
There are several advantages of the TIMS method. It has a simple design, is less expensive than other mass spectrometers, and produces stable ion emissions. It requires a stable power supply, and is suitable for species with a low ionization potential, such as Strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
(Sr), and Lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
(Pb).
The disadvantages of this method stem from the maximum temperature achieved in thermal ionization. The hot filament reaches a temperature of less than 2500 degrees Celsius, leading to the inability to create atomic ions of species with a high ionization potential, such as Osmium
Osmium
Osmium is a chemical element with the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-blacktransition metal in the platinum family, and is the densest natural element. Osmium is twice as dense as lead. The density of osmium is , slightly greater than that of iridium,...
(Os), and Tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
(Hf-W). Although the TIMS method can create molecular ions instead in this case, species with high ionization potential can be analyzed more effectively with MC-ICP-MS.
Multiple collector - inductively coupled plasma - mass spectrometry (MC-ICP-MS)
An MC-ICP-MS instrument is a multiple collector mass spectrometer with a plasma source. MC-ICP-MS was developed to improve the precision achievable by ICP-MS during isotope-ratio measurements. Conventional ICP-MSICP-MS
Inductively coupled plasma mass spectrometry is a type of mass spectrometry that is highly sensitive and capable of the determination of a range of metals and several non-metals at concentrations below one part in 1012...
analysis uses a quadrupole analyser, which only allows single-collector analysis. Due to the inherent instability of the plasma, this limits the precision of ICP-MS with a quadrupole analyzer to around 1%, which is insufficient for most radiogenic isotope systems.
Isotope-ratio analysis for radiometric dating
Radiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
has normally been determined by TIMS. However, some systems (e.g. Hf-W and Lu-Hf) are difficult or impossible to analyse by TIMS, due to the high ionization potential of the elements involved. Therefore these methods can now be analysed using MC-ICP-MS.
Magnetic sector mass spectrometry requires a high acceleration potential in order to properly resolve species with different masses. Since the ion beam is normally positive, a multi-collector ICP-MS (unlike conventional ICP-MS) needs to have an ion source up to 8000 V positive, in order to keep the analyzer at electrical ground. This was one of the engineering challenges of developing MC-ICP-MS. Magnetic sector mass spectrometry also requires an ion beam with a relatively small range in ion energy. This is achieved in MC-ICP-MS by using an electrostatic and/or quadrupole pre-filter, which allows the ion energy of the beam to be homogenized before entering the magnetic sector.
Moving Wire IRMS (MW-irMS)
Moving wire IRMS is useful for analyzing Carbon-13Carbon-13
Carbon-13 is a natural, stable isotope of carbon and one of the environmental isotopes. It makes up about 1.1% of all natural carbon on Earth.- Detection by mass spectrometry :...
ratios of compounds in a solution, such as after purification by liquid chromatography. The solution (or outflow from the chromatography) is dried onto a nickel or stainless steel wire. After the residue is deposited on the wire, it enters a furnace where the sample is converted to CO2 and water by combustion. The gas stream finally enters a capillary, is dried, ionized, and analyzed. This process allows a mixture of compounds to be purified and analyzed continuously, which can decrease the analysis time by a factor of four. Moving wire IRMS is quite sensitive, and samples containing as little as 1 nano-mole
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
of Carbon can yield precise (within 1‰) results.
Accelerator Mass Spectrometry (AMS)
For isotopes occurring at extremely low levels, accelerator mass spectrometryAccelerator mass spectrometry
Accelerator mass spectrometry differs from other forms of mass spectrometry in that it accelerates ions to extraordinarily high kinetic energies before mass analysis. The special strength of AMS among the mass spectrometric methods is its power to separate a rare isotope from an abundant...
(AMS) can be used. For example, the decay rate of the radioisotope 14C is widely used to date organic materials, but this approach is limited to relatively large samples no more than a few thousand years old. AMS extended the range of 14C dating to about 60,000 years BP, and is about 106 times more sensitive than conventional IRMS.
Applications
The variation outlined above has applications in hydrologyHydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
since most samples will lie between these two extremes. Given a sample of water from an aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
, and a sufficiently sensitive tool to measure the variation in the isotopic ratio of hydrogen in the sample, it is possible to infer the source, be it ocean water seeping into the aquifer or precipitation seeping into the aquifer, and even to estimate the proportions from each source.
Another application is in paleotemperature measurement for Paleoclimatology
Paleoclimatology
Paleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...
. For example one technique is based on the variation in isotopic fractionation of oxygen by biological systems with temperature.
Species of foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
incorporate oxygen as calcium carbonate in their shells. The ratio of the oxygen isotopes oxygen 16 and oxygen 18 incorporated into the calcium carbonate varies with temperature and the oxygen isotopic composition of the water. This oxygen remains "fixed" in the calcium carbonate when the forminifera dies, falls to the sea bed, and its shell becomes part of the sediment. It is possible to select standard species of forminifera from sections through the sediment column, and by mapping the variation in oxygen isotopic ratio, deduce the temperature that the forminifera encountered during life if changes in the oxygen isotopic composition of the water can be constrained.
In forensic science, research suggests that the variation in certain isotope ratios in drugs derived from plant sources (cannabis, cocaine) can be used to determine the drug's continent of origin.
See also
- Accelerator mass spectrometryAccelerator mass spectrometryAccelerator mass spectrometry differs from other forms of mass spectrometry in that it accelerates ions to extraordinarily high kinetic energies before mass analysis. The special strength of AMS among the mass spectrometric methods is its power to separate a rare isotope from an abundant...
- AtomAtomThe atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
- Bainbridge mass spectrometer
- IsoscapesIsoscapesIsoscapes are spatially explicit predictions of elemental isotope ratios that are produced by executing process-level models of elemental isotope fractionation or distribution in a Geographic Information System . The word isoscape is derived from isotope landscape and was first coined by...
- Isotope geochemistryIsotope geochemistryIsotope geochemistry is an aspect of geology based upon study of the relative and absolute concentrations of the elements and their isotopes in the Earth. Variations in the abundance of these isotopes, typically measured with an isotope ratio mass spectrometer or an accelerator mass spectrometer,...
- Isotopomer
- Table of nuclidesTable of nuclidesThe tables listed below provide information on the basic properties of all nuclides.* Neutron + Element 1 - Element 24 * Element 25 - Element 48 * Element 49 - Element 72...