ASMS 1984

From Mass Spec Terms

ASMS Committee on Nomenclature

San Antonio, 1984

The meeting of the Nomenclature Committee was held on May 26, 1984, and it was attended by 10 people including the Chairman. The Chairman gave a brief history of the actions of the Committee since 1979. The history was deduced from reports of the Committee meetings published in the Bound Volumes from 1979 through 1983. It was particularly pointed out that 370 and expressions referring to mass spectrometry have been defined and given in these issues of the Bound Volume, and it may be concluded that the Committee has been very active. It was also deduced from the report of the 1983 meeting of the Committee that action was required at the 1984 meeting on the terms listed on p. 970 of the 1983 Bound Volume under the heading, "Definitions for Consideration" and on the 58 terms given on pp. 904-909 of the 1982 Bound Volume starting with the terms under the heading "Secondary Ion Mass Spectrometry."

The Committee voted to accept all of the terms under consideration on p. 970 of the 1983 Bound Volume with the exception of the definition of Preformed Ions, which was deleted as being obvious and unnecessary. A small editorial change was made on Lhe definition for Average Mass. The Chairman regrets that the maker and seconder of the motion on these matters was inadvertently not recorded.

It was moved by J. Yergey and seconded .by J. Hiller not to accept any of the terms referring to Secondary Ion Mass Spectrometry given on pp. 904-907 of the 1982 Bound Volume. The motion carried. However, in addition it moved by T. Lehman and seconded by K. Busch that these terms and their definitions be given to the organizers of the conference on secondary ion mass spectrometry going to be held this Fall. The motion carried, and the Chairman asked Dr. Lehman to undertake theaction called for by the motion. He agreed to do this.

In the material received by the Chairman from the previous Chairman was a list of 268 terms relating to computers and computer technology. The correspondence examined by the Chairman seemed to imply that these terms should be considered at the 1984 meeting of the Committee. Consequently they were examined with as much care as was possible given the very large number of terms and the relatively limited time of the meeting. It was moved by H. Fales and seconded by J. Yergey that these terms not be accepted by the Committee. The motion passed unanimously.

It was moved by J. Watson and seconded by J. Yergey that the Chairman bring together all of the terms which have appeared in the Bound Volumes through 1983 (and including those approved at this meeting) to make one . complete list for easy reference by members of ASMS and mass spectrometrists in general. The Chairman agreed to do this, and the resulting list is included as pa.t of this report.

The Committee discussed the question of what should be the future actions of the Committee. In view of the large number of terms already defined, the sense of the meeting was not to consider any new category of terms for the next year. However, the Committee agreed to meet at the next ASMS meeting to consider further activities.

F.H. Field Chairman 6 June 1984


Combined List of Defined Terms

Analyzers

Electrostatic analyzer
A velocity focusing device composed of means for producing an electrostatic field perpendicular to the direction of ion travel. Effect is to bring to a common focus all ions of a given kinetic energy. Usually used in combination with a magnetic analyzer for mass analysis.
Magnetic analyzer
A direction focusing device composed of means for producing a magnetic field perpendicular to the direction of ion travel. Effect is to bring to a common focus all ions of a given momentum with the same mass to charge ratio.
Quadrupole analyzer
A mass filter consisting of means of creating a quadrupole fiel of a constant component and a varying component in such a manner as to allow transmission of only a selected mass-charge ratio,
Time of flight analyzer
A device consisting of a means to measure the flight time of particles with an equivalent kinetic energy over a fixed distance.
Wien analyzer
A velocity filter composed of means for creating crossed homogeneous electric and magnetic fields such that only ions of a fixed velocity are transmitted.
Mass resonant analyzer
A mass analyzer composed of means for mass dependent resonant energy transfer and measurement of the resonance frequency, power or ion current of the resonant ions. (The following are standard instrumental configurations utilizing one or more of the above techniques.)
Double focusing analyzer
The combination of a magnetic analyzer and electrostatic analyzer in either sequence to effect direction and velocity focusing.
Ion cyclotron resonance analyzer
A device to determine the mass of an ion by measuring its resonant frequency.
Ion trap analyzer
A mass resonance analyzer co'mposed of means for creating a three dimensional rotationally symmetric quadrupole field capable of storing ions at selected masses,
Mass spectrometer configurations
Multianalyzer instruments should be named or the analyzers in the sequence in which they are traversed by the ion beam, where B is for a magnetic analyzer, E for an electrostatic analyzer, Q for a quadrupole analyzer, TOF for time of flight analyzer, and ICR for an ion cyclotron resonance analyzer. For example, we have a BE mass spectrometer ("reversed" geometry double focusing instrument), BQ mass spectrometer (hybrid sector and quadrupole instrument), EB Q (high resolution followed by a quadrupole). Note that a triple quadrupole which has il'.!2, mass analyzers is a QQ mass spectrometer. Problem: Time of flight, simultaneously or sequentially with other mass analyzers.

Data System

. . .

Ionization Nomenclature

Electron ionization
This is the term used to describe ionization of any species by electrons. The process may, for example, be written
M + e- → M+· + 2e-.

for atoms or molecules, .. and M + e- → M+ + 2e- for radicals.

Photo-ionization
This is the term generally used to describe ionization of any species
by photons. The process may, for example, be written


[Note: Electrons and photons do not "impact" molecules or atoms. They interact with them in ways that result in various electroriic excitations including ionization. For this reason it is recommended that the terms 'electron impact' and 'photon impact' be not used).
Field ionization
This term relates to the removal of electrons from any species by interaction with a high electrical field.
Field desorption
This term is used to describe the formation of ions in the gas phase from a material deposited ona solid surface (known as an 'emitter') in the presenceof a high electrical field. 'Field desorption' is an ambiguous term because it implies that the electric field desorbs a material as an ion from some kind of emitter on which the materialis deposited. There is growing evidence that some of the ions fanned are due to themal ionization, some to field ionization of vapor evaporated from material on the emitter. Because there is little or no ionization unless the emitter is heated by an electric current, 'field desorption' is a misnomer. The term is however firmly implanted in the literature and most users (by no means all) understand what is going on regardless of the implications of the term. In addition, no better simple term has been suggested to take its place and so; reluctantly, it is recommended that it be retained.
Chemi-ionization and chemical ionization are two terms which should not be used inter-changeably.
Chemi-ionization
refers to a process whereby gaseous molecules are ionized when they interact with other internally excited gaseous molecules or molecular moieties.
Chemical ionization
concerns the process whereby new ionized species are formed when gaseous molecules interact with ions. The process may involve transfer of an electron, proton or other charged species to or between the reactants. When a positive ion results from chemical ionization, the term may be used without qualification. When a negative ion results, the term negative ion chemical ionization should be used.
Surface ionization
takes place when an atom or molecule is ionized when it interacts with a solid surface. Ionization only.occurs when the work function of the surface, the temperature of the surface, and the ionization energy of the atom or molecule nave an appropriate relationship.
Thermal ionization
takes place when an atom or molecule interacts with a heated surface or is in a gaseous environment at high_ temperatures.: [Examples of the latter may be a capillary a_rc plasma, a microwave plasma, or an inductively coupled plasma].
Atmospheric pressure ionization
is an ambiguous term. In essence, it is used to describe chemical ionization at atmospheric pressure. It is recommended that use of the term should be discouraged.
Spark (source) ionization
occurs when a solid sample is vaporized and partially ionized by an intermittent electric discharge. Further ionization occurs in the discharge when gaseous atoms and small molecular moieties interact with energetic electrons in the intermittent discharge. It is recommended that the word 'source' be dropped from this term.
Auto-ionization
occurs when an internally supra excited atom or molecular moiety loses an electron spontaneously without further interaction with an energy source. (The state of the atom or molecular moiety is known as a pre-ionization state).
Associative ionization
occurs when two excited gaseous atoms or molecular moieties interact and the sum of their internal energies is sufficient to produce a single, additive ionic product.
Multi-photon ionization
occurs when an atom or molecule and their concomitant ions have energy states whereby the energy in two or more photons can be absorbed.
Penning ionization
occurs through the interaction of two or more neutral gaseous species at least one of which is internally excited.
Charge exchange (charge transfer ionization) ionization
occurs when an ion/atom or ion/molecule reaction takes place in which the charge on the ion is transferred to the neutral species without any dissociation of either.
Ion-pair formation
involves an ionization process in which a positive fragment ion and a negative fragment ion are the only products.
Ionization cross section
This is a measure of the probability that a given ionization process will occur when an atom or molecule interacts with an electron or a photon.
Electron attachment
A resonance process whereby an external electron is incorporated into an atomic or molecular orbital of an atom or molecule.
Ionization energy
This is the minimum energy of excitation of an atom, molecule or molecular moiety required to remove an electron in order to produce a positive ion.
Vertical ionization
This is a processs whereby an electron is removed from a molecule in its ground or an excited state so rapidly that a positive ion is produced without change in the positions or momenta of the atoms. The resultant ion is often in an excited state.
Adiabatic ionization
A process whereby an electron is removed from the ground state of an atom or molecule producing an ion in its ground state.
Ionization
A process which produces an ion from a neutral atom or molecule.
Dissociative ionization
Im ionization process in which a gaseous molecule decomposes to form products, one of which is an ion.
Ionic dissociation
A decomposition of an ion into another ion of lower formula-weight and one or more neutral species.
Ionization efficiency
is the ratio of the number of ions formed to the number of electrons or photons used.
An ionization efficiency curve
shows the number of ions produced as a function of the energy of the electrons or photons used to_produce ionization.
Laser ionization
occurs when a sample is irradiated with a laser beam. In the irradiation of gaseous samples, ionization occurs via a single-or multi-photon process. In the case of solid samples, ionization occurs via_ a thermal process.
Desorption Ionization (DI)
General term to encompass the various procedures (secondary ion mass spectrometry, fast atom bombardment, californium fission fragment desorption, thermal desorption) in which ions are generated directly from a solid sample by energy input.

Types of ions

Positive ion
This is an atom, radical, molecule or molecular moiety which has lost one or more electrons thereby retaining an electrically positive charge. The use-of the term cation as an alternative is not recommended. The use of mass ion is not recommended.
Negative ion
An atom, radical, molecule or molecular moiety in the vapor phase which has gained one or more electrons thereby acquiring an electrically negative charge. The use of the term anion as an alternative is not recommended.
Singly-, Doubly-,

Triply-etc. Charged Ion These terms are used to describe an atom, molecule or molecular moiety which has gained or lost one, two, three or more electrons. The term multiply-charged ion is used to refer to ions that have gained or lost more than one electron where the number of electrons lost or gained is not designated.

Parent ion
An electrically charged molecular moiety which may dissociate to form fragment. one or more of which may be electrically charged, and one or more neutral species. A parent ion may be a molecular ion or an electrically charged fragment of a molecular ion.
Fragment ion
An electrically charged dissociation product of an ionic fragmentation. Such an ion may dissociate further to form other electrically charged molecular or atomic moieties of successively lower formula weight. (See also Daughter lon).
Daughter ion
An electrically charged product of reaction of a particular parent ion. In general such ions have a dfrect relationship to a particular precursor ion and indeed may relate to a unique state of the precursor ion. nnThe reaction need not necessarilyinvolve fragmentation. ft could, for example involve a change in the number of charges carried. Thus, all fragment ions are daughter ions but not all daughter ions are necessarilY fragment ions.
Rearrangement ion
An electrically charged dissociation product, involving a molecular or parent ion, in which atoms or groups of atoms have transferred from one portion of a molecule or molecular moiety to another during the fragmentation process.
Stable ion
An ion which is not sufficiently excited to dissociate into a daughter ion and associated neutral fragment(s) or to react further in any other way.
Unstable ion
An ion which is sufficiently excited to dissociate within the ion source.
Metastable ion
An ion which is sufficiently excited to dissociate into a particulardaughter ion and neutral species during the flight from the ion source to the detector. The dissociation is most readily observed when it takes place in one of the field-free regions in a mass spectrometer.
Precursor ion
This term is synonymous with parent ion.
Product ion
This term is synonymous with [daughter ion]].
Molecular ion
An ion formed by the removal (positive ions) or addition (negative ions) of one or more electrons from a molecule without fragmentation of the molecular structure. The mass of lhis ion corresponds to the sum of the masses of the most abundant naturallyoccurring isetopes of the various atoms that make up the molecule (with a correction for the masses of the electrons lost or gained). For example, the mass of the molecular ion of ethyl bromide, C2H5Br will be 2xl2 plus Sxl.0078246 plus 78.n91839 minus the mass of the electron (me)-This is equal to 107.95751 u -mn, u being the unit of atomic mass based on the standard that the mass of the isotope 12c = 12u exactly.
Isotopic molecular ion
A molecular ion containing one or more of the less abundant naturally occurring isotopes of the atoms that make up the molecular structure. Thus, for ethyl bromide there exist molecular isotope ions such as 13CCH5Br+ , C2H4D Br+ C2Hsn81Br+ , 13C2H581Br+ etc. ,
Isotopic ion
Any ion containing one or more of the less abundant naturallynoccurring isotopes of the elements that make up its structure.
Isotopically enriched ions
When the abundance of a particular isotope is increased above the level at which it occurs in nature and is incorporated in a molecule the term "isotopically enriched ion" is used to describe any ion containing the enriched isotope.
Dimeric ion
An ion formed either when a chemical species exists in the vapor phase as a dimer and can be detected as such, or when a molecular ion can attach to a neutral molecule within the ion source to form an ion such as [2M]n+. where M represents the molecule.
Protonated molecule
An ion formed by interaction of a molecule with a proton abstracted from an ion, as often occurs in Chemical Ionization according to the reaction : M + XH+ + MH+ + X. The symbolism [M+H]+ may also be used to represent the protonated molecule.
[Note : The widely-used term 'protonated molecular ion' to "describe the MH+ ion is not recommended. It suggests an association product of a proton with a molecularion]-..
Adduct ion
An ion formed by interaction of two species, usually an ion and a molecule, and often within the ion source, to form an ion containing all the constituent atoms of one species as well as an additional atom or atoms.
Cluster ion
An ion formed by the combination of two or more molecules of a chemical species often in association with a second species. For example, [ (H2OlnHJ + is a cluster ion.
Radical ion
An ion containing an un-paired electron which is thus both an ion and a free radical. The presence of the odd electron is denoted by placing a dot alongside the symbol for the charge. Thus, CzHG+ and SFG- are radical ions.
Odd-electron ion
This term is synonymous .with radical ion.
Even-electron ion
An ion containing nonun-paired electrons, for example CH3 in its ground state.

Ion/molecule reactions

Ion/neutral reaction
A process wherein a charged species interacts with a neutral reactant to produce either chemically different species or changes in the internal energy of one or both of the reactants. (NB. The term ion/neutral reaction is not ideal, simply because the word neutral is not a noun. However, any alternatives such as ion/neutral-species are so clumsy as to seem unlikely to be generally accepted).
Ion/molecule reaction
An ion/neutral reaction in which the neutral species is a molecule.
Charge inversion reaction
An ion/neutral reaction wherein the charge on the reactant ion is reversed in sign.
Charge transfer reaction
An ion/neutral reaction wherein the total charge on the reactant ion is transferred initially to the reactant neutral species so that the reactant ion becomes a neutral entity.
Partial charge transfer reaction
An ionn/neutral species reaction wherein the chargenon a multiply-charged reactant ion is reduced.
Charge stripping reaction
An ion/neutral reaction wherein the charge on the reactant ion is made more positive.
Charge permutation reaction
This is a general term to describe an ion/neutral reaction wherein there is a change in the magnitude and/or sign of the charges on the reactants.
(Note: Considering some of the possible reactions of ions M2+, M+ and M- with a neutral species N these would be categorised on the basis of the above definitions as follows:
M2+ + N → M+ + N (Partial charge transfer)
M+ + N → M2+ + N + e- (Charge stripping)
M- + N → M+ + N + 2e- (Charge stripping and charge inversion)
All are ion/neutral reactions and also charge permutation reactions].
Collision-induced dissociation
An ion/neutral process wherein the (fast) projectile ion is dissociated as a result of interaction with a target neutral species. This is brought about by conversion of part of the translational energy of the ion to internal energy in the ion during the collision.
Collisional activation
An ion/neutral process wherein excitation of a (fast) projectile ion is brought about by the same mechanism as in collision-induced dissociation. (The ion may decompose subsequently)n.
Collisional excitation
An ion/neutral process wherein there is an increase in the (slow) reactant ion's internal energy at the expense of the translational energy of either (or both) of the reacting species. The scattering angle may be large.
(Note: It is recommended that all three of the above terms should be retained).
Elastic scattering
An ion/neutral interaction wherein the direction of motion of the ion is changed, but there is no change in the total translational energy or internal energyof the collision partners.
Inelastic scattering
An ion/neutral interaction wherein the direction of motion of the ion is changed, and the total translational energy of the collision partners is reduced.
Elastic collision
A collision resulting in elastic scattering.
Inelastic collision
A collision resulting in inelastic scattering.
Superelastic collision
A collision in which the translational energy of the fast-moving collision partner is increased.
Ionizing collision
An ion/neutral reaction in which an electron or electrons are strippedfrom the ion and/or the neutral species in the collision. 'Generally, this term has come to be used to describe collisions cif fast moving ions with a neutral species in which the neutral species is ionized with no change in the number of charges carried by the ion. Care should be taken when this term is used to emphasize if charge stripping of the ion has taken place.
Association reaction (associative combination)
The reaction of a (slow moving) ion with a neutral species wherein the reactants combine to form a single ionized species.
Ion/neutral exchange reaction
In this reaction an association reaction is accompanied by the subsequent or simultaneous liberation of a different neutral species as product.
Translational spectroscopy
A technique to investigate the distribution of the velocity of product ions from ion/neutral reactions.
Ion energy loss spectra
Spectra that show the loss of translational energy of ions involved in ion/neutral reactions.
Impact parameter
The distance of closest approach of two particles if they had continued in their original direction of motion at their original speeds.
Interaction distance
The furthest distance of approach of two particles at which it is discernible that they will not pass at the impact parameter.
Charge exchange reaction
This term is synonymous with Charge Transfer Reaction.
Partial charge exchange reaction
This term is synonymous with partial charge transfer reaction.

Sample Introduction

Sample introduction system
This is a system used to introduce sample to a mass spectrometer ion source before and/or during analysis. (sample introduction system, introduction system, sample inlet system, inlet system, and inlet are synonymous terms.)
Reservoir inlet
This is an inlet system having an enclosed volume (the reservoir), with provision to evacuate the reservoir, to admit sample to the reservoir, and to allow gas or vapor from the reservoir to flow through a leak to the mass spectrometer ion source. A complete description of a reservoir inlet should include a description of the method by which the sample is introduced into the reservoir (e.g. with gas-metering, septum, fritted-disc, or teflon-cup introduction), an indication as to whether the leak provides viscous or molecular flow, and an indication whether the reservoir is heated.
Batch inlet
This is the historic term for a reservoir inlet. Reservoir inlet is preferred because a direct inlet probe is also a form of batch inlet. Batch gas inlet or batch vapor inlet is, however, a completely descriptive term.
Dual viscous-flow reservoir inlet
This is an inlet having two reservoirs, used alternately, each having a leak that provides viscous flow. This inlet is used for making precise comparisons of isotope ratios in two samples.
Continuous inlet
This is an inlet in which gas or vapor passes continuously into a mass spectrometer ion source, as distinguished from a reservoir inlet or a direct inlet probe.
Non-fractionating continuous inlet
This is a continuous inlet in which gas flows from a gas stream being analyzed to the mass spectrometer ion source without any change in the conditions of flow through the inlet or by the conditions of flow through the ion source.
Direct-inlet probe
This is a rod having a sample holder at one end, which is inserted into the vacuum system of a mass spectrometer through a vacuum lock, placing the sample near to, at the entrance of, or within the ion source, so that the sample can be vaporized after introduction to the vacuum system by heat from the ion source or by heat applied to the probe from an external source. (direct inlet probe, direct-introduction probe or direct-insertion probe are synonymous terms. The use of DIP as an abbreviation for these terms is not recommended.)
Vacuum-lock inlet
This is an inlet in which a sample is placed in a chamber, the chamber is pumped out, and a valve is opened so that the sample can then be introduced to the mass spectrometer ion source. A vacuum-lock inlet commonly uses a direct- inlet probe which passes through one or more sliding seals, but other kinds of vacuum-lock inlets are possible.
Extended direct-inlet probe
This probe provides for insertion of a sample on an exposed surface (such as a flat surface or a wire) into (rather than up to the entrance of) the ion source of a mass spectrometer. (This term is synonymous with direct-exposure probe.)
Crucible direct-inlet probe
With this probe, the sample is held in a cup-shaped device (the crucible) rather than on an exposed surface. A direct-inlet probe is assumed to be a crucible type unless otherwise specified.
GC/MS interface
This is an interface between as gas chromatograph and a mass spectrometer which serves to provide continuous introduction to a mass spectrometer ion source of effluent gas from a gas chromatograph during the period for which the effluent gas is to be analyzed.
Direct GC/MS
This is an interface in which the entire effluent from the gas chromatograph passes to the mass spectrometer ion source during an analysis, without any splitting of this effluent.
Splitter GC/MS interface
This is an interface in which the effluent from the gas chromatograph is divided before admisssion to the mass spectrometer, without enrichment of sample with respect to carrier gas.
Separator GC/MS interface
This is an interface in which the effluent from the gas chromatograph is enriched in the ratio of sample to carrier gas. (Separator, molecular separator, and enricher are synonymous terms.) A separator should generally be defined as an effusion separator, a jet separator, or a membrane separator.
Effusion separator (or effusion enricher).
This is an interface in which carrier gas is preferentially removed from the gas entering the mass spectrometer by effusive flow (e.g. through a porous tube or through a slit).
Jet separator
This is an interface in which carrier gas is preferentially removed by diffusion out of a gas jet flowing from a nozzle. (jet separator, jet-orifice separator, jet enricher and jet-orifice enricher are synonymous terms.)
Membrane separator
With this separator, the gas or vapor passes to the mass spectrometer through a semi-permeable membrane (e.g. a silicone membrane) which selectively transmits organic compounds in preference to carrier gas. (Membrane Separator, Membrane Enricher, Semi-Permeable Membrane Separator, and Semi-Permeable Membrane EnrTcher are synonymous terms.)
Solvent-divert system
This system is used in conjunction with an interface which permits temporary interruption of the flow from a gas chromatograph to a mass spectrometer by opening a valve to a pumping line, so that an effluent present at a high concentration (usually solvent) does not enter the mass spectrometer ion source at a high concentration.
Liquid chromatograph/mass spectrometer (LC/MS) interface
This interface is between a liquid chromatograph and a mass spectrometer which serves to provide continuous introduction to a mass spectrometer ion source of the effluent from a liquid chromatograph during the period for which the effluent is to be analyzed.
Moving belt (ribbon or wire) interface
With this interface, all or a part of the effluent from a liquid chromatograph is continously applied to a belt (ribbon or wire), which passes through two or more orifices, with differential pumping, into the mass spectrometer vacuum system; after which heat is applied, to remove the solvent, and then to evaporate the solute into the ion source.
Direct chemical ionization interface
With this interface, all or a part of a liquid chromatograph effluent passes continuously to the mass spectrometer, in which the solvent is used as a chemical ionization agent for ionization of the solute.

Scanning of spectra

Mass spectrum
A spectrum obtained when a beam of ions is separated according to the mass-to-charge (m/z) ratios of the ionic species contained within it.
[Note : A quadrupole mass spectrometer achieves separation of the various ionic species in this way].
Momentum spectrum
A spectrum _obtained when a beam of ions is separated according to the momentum-to-charge ratios of the ionic species contained within it.
[Note: A sector magnetic field achieves separation of the various ionic species in this way. If the ion beam is homogeneous in translational energy, as is the case with sector instruments, separation according to the m/z ratios is also achieved].
Ion kinetic energy spectrum
A spectrum obtained when a beam of ions is separated according to the translational energy-to-charge ratios of the ionic species contained within it.
[Note : A radial electric field achieves separation of the various ionic species in this way].
Magnetic field scan
The usual method of producing a momentum (mass) spectrum in instruments.
Accelerating voltage (high voltage) scan
An alternative method of producing a momentum (mass) spectrum in magnetic deflection instruments. This scan can also be used, in conjunction with a fixed radial electric field to produce an ion kinetic energy spectrum.
Linked scan
A scan, l'.n an" instrument comprising two or more analysers, in which two or more of the analyser fields are scanned simultaneously so as to preserve a predetermined relationship between parameters characterising these fields. often, these parameters are the field strengths, but may also be the frequencies in the case of analysers in which alternating fields are employed_ ..
Linked scan at constant B/E
A linked scan at constant B/E may be performed on a sector instrument incorporating at least one magnetic sector plus one electric sector. It involves scanning the magnetic sector field-strength B and the electric sector field strength E simultaneously, holding the accelerating voltage V constant, so as to maintain the ratio B/E at a constant value. This constant value is determined by the ratio of the two field strengths which transmit main-beam ions of predetermined mass:charge ratio; these preselected main-beam ions are the precursor ions whose fragment-ion spectrum is required. The fragmentation reactions so observed occur in a field-free region traversed before the two sectors scanned in this way.
[Notes: This terms should not be used without prior explanation of the meanings of B and E.

The term "B/E linked scan" is not recommended. It may suggest that the ratio B/E varies during the scan].

Linked scan at constant E2/V
A linked scan at constant E2/V may be performed on a sector instrument incorporating at least one electric sector plus one magnetic sector. It involves scanning the electric sector field E and the accelerating voltage V simultaneously, so as to maintain the ratio E2/V at a constant value, equal to the value of this ratio which transmits the main beam of ions through the electric sector. The magnetic sector field is set at a fixed value such. that main-beam ions of a pre.determined mass:charge ratio are transmitted by the magnet; these preselected main.beam ions are the precursor ions whose fragment-ion spectrum is required. The fragmentation reactions so observed occur in a field-free region traversed before the two sectors scanned in this way.
[Notes : This term should not be used without prior explanation of the meanings of E and V.

The term "E2/V linked scan" is not recommended].

Linked Scan at Constant B2 /V
A linked scan at constant B2 /E may be performed on a sector instrument incorporating at least one electric sector plus one magnetic sector. It involves holding the accelerating voltage fixed, and scanning the magnetic field Band the electric field E simultaneously so as to maintain the ratio 82 /E at a constant value. This constant value corresponds to the ratio of the two fields which 'transmit main-beam ions of predetermined mass:charge ratio; these preselected main-beam ions are the fragment ions whose precursor-ion spectrum is required. The fragmentationreactions thus observed occur in a field-free region traversed before the two sectors scanned in this way.
[Notes : This term should not be used without prior explanation of the meanings of Band E. The term "B2 /Elinked scan" is not recommended] .
Linked Scan at Constant B l[ (E/E0)]l /E A 1 inked scan at constant B[l -(Ee/E0)]'/E may

be performed on a sector instrument incorporating at least one electric sector plus one magnetic sector. It involves holding the accelerating voltage fixed, and scanning the magnetic field Band electric field E simultaneously, so as to maintain the quantityB[l -(E/Eo)]l/E at a constant value. This constant value is equal to B3/E0 , where E0 and B3 are respectively the electric sector field and magnetic sector field required to transmit m; ions in the main ion-beam; me3 represents the mass (m1 -m2) of the selected neutral fragment whose precursor ion spectrum is required. The fragmentationreactions so observed occur in a field-free regio. traversed before the two sectors scanned in this way.

[Note: This term should not be used without prior explanation of the meanings of B, E and E0 .
The term "B [l -(E/E0)] '/E linked scan" is not recommended].

The above three definitions are merely examples of the types of linked scan that might be used. Any other linked scans can readily be defined inna similar manner.

Fixed Precursor Ion Scans
1. Mass Selection followed by Ion .Kinetic Energy Analysis

If a precursor (parent) ion is selected, for example by a magnetic sector, all product ions formed from it in the field-free region between the magnetic sector and a following electric sector can be identified by scanning an ion kinetic energy spectrum.

2. Linked Scan at Constant B/E or at Constant E2 /V
Both of these linked scans give a spectrum of all product (daughter) ions formed from a preselected precursor (parent) ion.
Fixed Product-Ion Scans
1. High Voltage Scan.
2. Linked Scan at Constant B2/E.
Both 1. and 2. give. a spectrum of all precursor (parent) ions that fragment to yield a pre-selected product (daughter) ion.
Fixed Neutral Fragment Scans 1 The linked scan at constant B[l -(E.'E0)]'/E gives a spectrum of all product (daughter)ions that have been formed by loss of a pre-selected neutralfcagment from any precursor(parent) ions.

[Note : The above definitions. have all been given with reference to sector instruments; linked scans to give similar information have also been devised for instruments incorporating one or more quadrupoles].

2E Mass Spectrum Processes of the partial charge-transfer type 2+ + N+

m + N . m + occurring in a collision cell (containing a gas, N) located in a field-free region preceding a magnetic and electric sector combination placed in either order, may be detected as follows.

If the instrument slits are wide, and if the electric sector field Eis set to twice the value required to transmit the main ion-beam, the only ions to be trans.mitted will be those with a kinetic energy/charge ratio twice, or almost exactlytwice, that of the main ion-beam. The product ions of the process shown fulfill this condition. If the magnetic field Bis scanned, a mass spectrum of such singly.charged product ions, and thus of their doubly-charged precursors, is obtained. Such a spectrum is called a 2E mass spectrum.

E/2 Mass Spectrum Processes of the charge-stripping type

m+ + N → m2+ + N + e- occurring in a collision cell (containing a gas N) located in a field-free regionpreceding a magnetic and electric sector combination placed in either order, may be detected as follows. If the instrument slits are wide and if the electric sector field Eis set to half the value required to transmit the main ion-beam, the only ions to be transmitted will be those with a kinetic energy/charge ratio half, or almost exactly half, that of the main ion-beam. The product ions of the charge-stripping process fulfill this condition. If the magnetic field Bis scanned, a mass spectrum of such doubly-charged product ions, and thus of their singly-charged precursors, is obtained. Such a spectrum is called an E/2 mass spectrum.

. [Note Interference from product ions from processes of _the type + m1 + -m2) where m2 . 0.5 m1, can arise in E/2 mass spectra]. Charge Inversion Mass Spectrum Charge inversion processes of the types or m-+ N → m+ + N + 2e. respectively, occurring in a collision cell (containing a gas, N) located in a field.fr_ee region preceding a magnetic and electric sector combination placed in either order, may be detected as followsn.

If the instrument slits are wide, and if the connections to the two sectors, appropriate to transmission of either positive or negative main-beam ionS, are simply reversed, the negative or positive product ions of the two processes,respectively, will be transmitted. If the magnetic field is scanned, a spectrumof such product ions will be obtained, and this spectrum is called a charge-inversion mass spectrum. These spectra are sometimes referred to as -E and +Enspectra, respectively.

[Note : The terms "2E, E/2, -E or +E mass spectrum" should not be used without priorexplanation of the meaning of 2E, E, +E or -E]n.

Vacuum

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