ASMS NOMENCLATURE COMMITTEE WORKSHOP .
One Workshop was held on Tuesday, June 8, 1982, which was co-sponsored by the ASTM El4.10 subcommittee on nomenclature. Due to various committments, those who volunteered last year to supply terms and definitions for the 1982 meeting were either unable to do so or could not do so until a few months prior to the meeting. This prevented the list of terms from being circulated until the day of the Workshop. For this reason, it was decided that the attached list be published in the bound volume of this year's meeting, and that comments on these terms be solicited from the ASMS membership. It was also decided that a separate coyer letter be sent to the membership alerting them to the list and the request for their comments.
A letter was read by Prof. Burnaby Munson regarding the view of the ASMS Board of Directors on the list of definitions produced at last year's Workshops. This letter is reproduced in part below. "The Board of Directors of ASMS approves the list of terms as presented in the Bound Volume of Abstracts for the 1981 meeting subject to periodic review and extension by the Nomenclature Committee and the Board, such that this shall be a living document. The Board recommends that authors' usage conform to this nomenclature."
All comments on this year's list of definitions should be sent to:
Doug Cameron Science and Technology Div.
Union Oil Company
P. 0. Box 76 Brea, CA 92621
All comments received prior to December 31, 1982, will be considered for inclusion into the list, and a revised version of the definitions will be sent to all interested persons prior to next year's meeting.
Doug Cameron Chairman
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 constant velocity. 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 constant momentum. Quadrupole Analyzer. A true mass filter consisting of means of creating a quadrupole field of a constant component and a varying component in such a manner as to allow transmission of only a selected mass to charge ratio.
Time of Flight. An ion travel time device consisting of a means to measure the flight time of ions with an equivalent kinetic energy over a fixed distance. Hien Analyzer. A velocity filter composed of means for creating a crossed homogeneous electric and magnetic field such that only ions of a fixed velocity are transmitted. Mass Resonant Spectrometer. 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 Mass Spectrometer . The combination of a magnetic analyzer and electrostatic analyzer in either sequence to effect direction and velocity focusing. Ion Cyclotron Resonance Spectrometer. A device to determine the mass of an ion by measuring its resonant frequency. Ion Trap Mass Spectrometer. A mass resonance spectrometer composed 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 for the mass analyzers in the sequence in which they are traversed by the ion beam. Using B for a magnetic analyzer, E for an electrostatic analyzer, Q for a quadrupole analyzer we have a BE mass spectrometer ("reversed" geometry double focusing instrument), BQ mass spectrometer (hybrid sector and quadrupole instrument), EBQ (high resolution followed by a quadrupole). Note that a triple quadrupole which has two. mass analyzers is a QQ mass spectrometer. Problem: Time of flight, simultaneously or sequentially with other mass analyzers.
- 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. Note: Intent is to establish a broad term analogous to chemical ionization which also encompasses a group of related ionization processes. 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
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 continously into a mass spectrometer ion source, as distinguished from a Reservoir Inlet or a Direct
- ]]Inlet Probe]]
Non-Fractionating Continuous Inlet. This 1s 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 Interferface
- 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 splittinq 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, Molecjlar 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.
- 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.
- Collision-Induced Dissociation (CID)
- The fragmentation of a polyatomic ion due to the collision of the ion with a target, usually a neutral gas molecule. (Collision Activated Dissociation (CAD) and Collisional
Activation (CA) are synonomous terms, but Collisionai Activation is not recommended.)
Collisional Activation (CA)
- This refers to the increase in internal energy of an ion as the result of a collision between the ion and a target.
SECONDARY ION MASS SPECTROMETRY (SIMS)
(The terms in this section have been provided entirely by ASTM Subcommittee E42.06 and are part of a list which is presently under consideration by this subcommittee. Their contribution is gratefully acknowledged.)
Analysis Area. The area of the specimen from which the secondary ion signal is accepted.
Angle of Incidence. The nominal angle between the incident Primary Ion Beam, and the normal to the original sample surface.
Angular Distribution. The variation of Secondary Ion Yield as a function of emission angle from the specimen.
Background Signal. Signal from both the continuum background on either side of the mass of interest and from species not completely resolved from the mass of interest.
Channeling. The process by which particles preferentially penetrate along crystallographic directions because of the long range atomic order in a crystalline specimen. Charge Neutralization. A technique in which a surface under ion bombardment is maintained at a constant potential by compensating for any accumulated charge.
Collection Angle. The angle between the normal to the original sample surface and the secondary ion collection optics.
Collision Cascade. A sequential energy transfer between excited atoms moving through a solid as a result of bombardment by an energetic primary ion.
Crater Wall Effect. A potential interference by secondary ions which originate from depths shallower than the maximum depth of the crater formed by ion bombardment.
Depth Profile. A plot of secondary ion signal as a function of sputtering time as a representative measure of the relative distribution of that species as a function of depth.
Depth Resolution. The depth range over which the secondary ion signal for one species increases from 10 to 90% at an ideally sharp interface between two dissimilar media.
Detection Limit. The lowest concentration of a substance which may be detected, i.e. the concentration which yields a signal twice the standard deviation of the background signal at the mass of the detected species. Contributions from both a continuum background and species of interfering mass must be included in the background measurement. The background ideally should be determined from an identical specimen except that it contains none of the constituent being determined.
Dynamic SIMS. SIMS analysis at sufficiently large primary ion currents such that more than one mono-layer of material is removed during the analysis.
Energy Distribution. A plot of the number of secondary Ions of a particular species leaving the sample surface as a function of the energy of those ions.
Equilibrium Composition. The steady state surface composition produced by sputter- etching a homogeneous sample under fixed conditions for the vacuum ambient and the primary ion beam.
Fractional Sputter Yield. The Sputter Yield of a particular component with respect to the total ion yield in a multicomponent matrix. Interface Width. The measured distance over which a 10 to 9O5S change in composition is measured at the junction of two dissimilar matrices.
Ion Beam. A directed flux of charged atoms or molecules.
Ion Beam Current. The measured total ion current incident upon the specimen.
Ion Beam Current Density. The current incident on the specimen per unit area.
Ion Beam Energy. The energy of the ions incident on the specimen surface, expressed in kilo electron volts, KeV.
Ion Implantation. The introduction and retention of an energetic ion within a target material.
Ion Neutralization. A process in which a charged species is converted into a neutral species.
Knock-In. The movement of a constituent of the target deeper into the target matrix as a result of recoil collisions with the primary ion beam.
Matrix Effect. The change in Sputtering Yield, Fractional Sputter Yield, ion yield or other experimental quantities which are caused by the difference in composition or structure between various samples. Molecular Ion (in SIMS). A charged multi-atom species detected in the secondary ion emission.
Negative Ion Yield. The number of negative ions sputtered from a target per incident ion of given mass, energy, charge, and angle of incidence. Positive Ion Yield. The number of positive ions sputtered from a target per incident ion of given mass, energy, charge, and angle of incidence.
Preferential Sputtering. The phenomena which occurs when the Fractional Sputter Yield for a species is different from the fractional composition of that species in the specimen.
Primary Ion Beam. A beam of charged particles incident on the sample which causes removal of the surface by sputtering. Primary Ion Beam Profile. The spatial distribution of the primary ion current in a plane perpendicular to the primary beam axis.
Raster. The periodic deflection of an ion beam.
Sample Charging. The accumulation of electrical charge on the sample caused by bombardment by a charged species. Secondary Ions. Ions ejected from a sample surface as a result of sputtering by the primary ion beam. Secondary Ion Signal Gating. The process of accepting secondary ion signal from only a portion of the sputtered area of the sample to avoid crater wall effects.
Secondary Ion Yield. The number of positive or negative ions sputtered from a target per incident, ion of given mass, energy, charge and angle of incidence. Selected Area Aperture. The mechanical equivalent of signal gating commonly used in stigmatic mass spectrometers. Selective Sputtering. The same as Preferential Sputtering. Sensitivity Factor. The factor used to convert the net counts per unit time, for a particular species, matrix and experimental conditions, to concentration. Signal to Background. The ratio of signal above background to that of the background.
- Signal to Noise Ratio
- The ratio of signal above background to either the standard
deviation of the signal including background, or one fifth the maximum variation in the signal including background.
- SIMS Ion Image
- The x-y distribution of a particular species sputtered from the sample surface representing the concentration distribution of that substance over the sample surface.
Sputter Rate. The amount of material removed per unit time as a result of ion bombardment.
- The average number of particles ejected from a sample surface per primary ion. Static SIMS. SIMS analysis at sufficiently small primary ion current density such
that less than one mono-layer of material is removed during the analysis.
- Target Current. The current striking the sample during primary ion bombardment. Useful Ion Yield. The ratio of ions detected to atoms sputtered from the analysis
Zone of Mixing. The layer of the target surface within which the primary beam causes atomic motion. Integer Ion m/z Values. Two definitions are proposed.
1. The set of positive integers, produced by appropriate changes in the magnitude of at least one of the independent variables in the laws-of-motion applicable to a given geometry instrument.
2. The set of positive integers generated by assigning integer values to the members of the sets of singly-charged homologous ions in the mass spectrum of a reference substance. This m/z scale establishes the integer m/z values for the ions in the mass spectra of other substances by the mathematical process of rounding these latter values to the nearest integer.
Integer Ion Mass. The integer ion m/z value multiplied by the number of charges on the ion.
Nominal Ion Mass. Let a(j) and MN(j) represent the atomic coefficients and the mass numbers, respectively, of the X(j) nuclides comprising a given formula. The nominal ion mass is thus defined by the expression m NMX(i)a(1)....xWaW-Xf»;arBj = z aw-ma)
Calculated Ion Mass and Associated Ewov. Let a(j) and M(j) represent the atomic coefficients and the masses, respectively, of the X(j) nuclides comprising a given formula. Let a.., .. be the variance in MCjV and M represent the rest mass of the electron. The following expressions then define the calcu.lated ion mass and its associated standard error, respectively. 1)Warm; . m k ^
- Calculated Ion m/z Value and Associated Error
- The calculated ion mass divided by the number of charges on the ion. The standard error is +(<jj..,/z).
Experimental Ion m/z Value and Associated Error. The experimental ion m/z value is the mass to charge ratio determined at a resolution R using a given mass spectrometer. Let the resolution be R = m/z/&[m/z) where t(m/z) is the width of the peak due to an ion having a mass-to-charge ratio of m/z at 5% of its height. If the peak shape is Gaussian, then b,(m/z) = 4.9 o where o is the standard deviation in the mass-to-charge ratio of the ions defining a given peak. The contribution of the ion statistics to the ppm standard deviation in m/z is thus 106 10 m/z " (4.9)(R)(N."NJ* where N. is the number of ions" in the peak and N is the number of scans averaged.
- Experimental Ion Mass;The experimental ion m/z value multiplied by the number of charges on the ion.
Error in the Experimental Ion Mass. Let Eft(i3j) be the experimental deter.mination of the known mass of the Jth ion, CMfoV, in the ith scan of the spectrum of a known substance acquired at a resolution R. For Nfl scans of the spectrum, the average ppm error in determining CMCjV, E(j)t and its associated standard deviation, ar/.i, are given by the following equations, respectively. 106 CMW - EM(i,jM) iou N -1 The root-mean-square (rms) error, ov, in the experimental errors for all j ions, which is a measure of the overallaccuracy in mass measurement at the resolution R, is The quantity ov can also be calculated using the values of °m/? calculated from N., N , and R in the equation defining E(j). 8 Random and Systematic Contributions to the Error. Let r be the random contri.bution to the rms error in mass measurement for a single scan and e be the systematic contribution to the error. Let ov' and ov be the rms errors for a single scan of the spectrum and for the average spectrum obtained from N scans of the spectrum. The following equations express ov' and ov as functions of r, e3 and N , L L S Or' = r + 8
Error Tolerance for Formula Acceptability. Let be the average experi.mental mass and CM be the calculated mass for the formula under consideration. The error tolerance for formula acceptability, (ET), is defined by the following equation where N 1B a positive integer. ET = |CM - | <_ 10"6-N.oE-