Abstract: A method of separating ions according to their time of flight is provided comprising: a. providing an analyser comprising two opposing ion mirrors, each mirror comprising inner and outer field-defining electrode systems elongated along an analyser axis with the outer field-defining electrode system surrounding the inner field-defining electrode system and creating therebetween an analyser volume; b. injecting ions into the analyser volume or creating ions within the analyser volume so that they separate according to their time of flight as they travel along a main flight path whilst undergoing a plurality of axial oscillations in the direction of the analyser axis and a plurality of radial oscillations whilst orbiting about one or more inner field-defining electrodes; c. the plurality of axial oscillations and plurality of radial oscillations causing the separated ions to intercept an exit port after a predetermined number of orbits.

Abstract: A method and apparatus are described herein for the interface of an ion mobility spectrometer (IMS) to a mass spectrometer (MS) that utilizes collisional focusing, through internal modification. Commercial standalone IMS instrumentation cannot be combined in tandem with a commercially available MS that utilizes collisional focusing due to the physics of the differentially pumped interface of the MS being an unsuitable environment for an IMS measurement. The invention provides for transfer of the ion beam from the IMS to the MS without distortion of the chemical species or temporal profile due to large scale collisions in the differentially pumped interface, by increasing the electric field strength between the orifice and skimmer, and decreasing the pressure in the differentially pumped interface, thereby reducing the number of background gas collisions encountered by the ion beam during transit from the IMS to the MS.

Abstract: A system for measuring size segregated mass concentration of an aerosol. The system includes an electromagnetic radiation source with beam-shaping optics for generation of a beam of electromagnetic radiation, an inlet sample conditioner with adjustable cut-size that selects particles of a specific size range, and an inlet nozzle for passage of an aerosol flow stream. The aerosol flow stream contains particles intersecting the beam of electromagnetic radiation to define an interrogation volume, and scatters the electromagnetic radiation from the interrogation volume. The system also includes a detector for detection of the scattered electromagnetic radiation an integrated signal conditioner coupled to the detector and generating a photometric output, and a processor coupled with the conditioner for conversion of the photometric output and cut-size to a size segregated mass distribution.

Abstract: A method of analyzing milk components having the steps of collecting a milk sample, ionizing the milk sample, and using an ion mobility spectrometer to detect predetermined components within the ionized milk sample, wherein the ion mobility spectrometer is positioned within a milking system from which the milk sample is taken.

Abstract: An algorithm-based system and method for tandem mass spectrometry data acquisition in which multiple precursor ion attributes, such as mass, intensity, mass-to-charge ratio and charge state, as well as results from previously performed mass spectrometry scans, are used to determine the likelihood of identification for each precursor ion. This information is then used to prioritize subsequent tandem mass spectrometry events, such as which precursor ions are to be fragmented and undergo further mass spectrometry analysis. By interrogating precursor ions in order of probability of successful identification, an increase in identified proteins and peptides is achieved.

Abstract: A method of determining a coefficient for converting an analog current value into a pulse count value in an inductively coupled plasma mass spectroscopy apparatus (ICP-MS) is described. The ICP-MS is configured to generate the pulse count value and the analog current value as a signal intensity indicating a density of an element in a sample to be measured.

Abstract: A mass spectrometer is provided including: a collision chamber of generating fragment ions by superimposingly applying an AC voltage and a first DC voltage between linear multipolar electrodes, and accelerating the fragment ions by applying a second DC voltage between a front stage electrode and a later stage electrode; a mass spectrometer unit of carrying out mass separation of the fragment ions; and a control unit of determining the second DC voltage based on the mass-to-charge ratios such that the rates of the fragment ions in the collision chamber become equal regardless of the mass-to-charge ratios. Herein, the control unit increases the second DC voltage as the mass-to-charge ratios selected by the mass spectrometer unit become larger. This allows the mass window to be wider even when a DC electric field is generated in order to solve a crosstalk drawback, in the movement direction of the molecular ions.

Abstract: An analytical instrument has a sample introduction system for generating a stream of particles from a sample and an ionization system for receiving the particles. The ionization system is operable to atomize the particles received from the sample introduction system and ionize atoms from the atomized particles. The instrument has an ion pretreatment system and a magnetic sector mass analyzer comprising an array detector. The ion pretreatment system is adapted to transport ions generated by the ionization system to the mass analyzer. The mass analyzer is adapted to detect a transient signal of at least one element from individual particles from said stream by performing mass analysis on the ions from the atomized particles. The magnetic sector mass analyzer is adapted determine an amount of said at least one element from an individual particle using the transient signal detected during mass analysis of the ions from said individual particle.

Abstract: In an ion detector, power supplies (21 through 23) generating independently controllable voltages are provided to respectively apply voltages to first to fifth dynodes (11 through 15), a final dynode (16), and an anode (17) in a secondary electron multiplier (10). Furthermore, the signal from the anode (17) is extracted, and the signal from the fifth dynode (15), which has a low electron multiplication rate, is extracted. These two signals are concurrently converted into digital values, taken in by a data processing unit (34), and stored in a data storage unit (35). When a mass spectrum is created in the data processing unit (34), the two detected data for the same time are read out and the presence or absence of signal saturation or waveform deformation is determined from the values of one of the detection data. If there is a high probability of signal saturation, the detection data based on the signals in the intermediate stages are selected, and the level of the selected data is corrected.

Abstract: The present invent provides a particle detector for counting and measuring the flight time of secondary electrons and scattered ions and neutrals and to correlate coincidences between these and backscattered ions/and neutrals while maintaining a continuous unpulsed microfocused primary ion beam for impinging a surface. Intensities of the primary particle scattering and secondary particle emissions are correlated with the position of impact of the focused beam onto a materials surface so that a spatially resolved surface elemental and electronic structural mapping is obtained by scanning the focused beam across the surface.

Abstract: There is provided a pulser, a time of flight mass spectrometer system comprising the same, and a method of analyzing the ions using the pulser. The pulser comprises a first positive switch for coupling and decoupling a first electrode of the accelerator assembly to a first positive voltage; a first negative switch for coupling and decoupling the first electrode to a first negative voltage; and, a first bipolar switch for alternately coupling and decoupling the first electrode to a third voltage.

Abstract: A system according to one embodiment includes a particle accelerator that directs a succession of polydisperse aerosol particles along a predetermined particle path; multiple tracking lasers for generating beams of light across the particle path; an optical detector positioned adjacent the particle path for detecting impingement of the beams of light on individual particles; a desorption laser for generating a beam of desorbing light across the particle path about coaxial with a beam of light produced by one of the tracking lasers; and a controller, responsive to detection of a signal produced by the optical detector, that controls the desorption laser to generate the beam of desorbing light. Additional systems and methods are also disclosed.

Abstract: Aspects of the present invention are directed generally toward atom probe and three-dimensional atom probe microscopes. For example, certain aspects of the invention are directed -toward an atom probe or a three-dimensional atom probe that includes a sub-nanosecond laser to evaporate ions from a specimen under analysis and a reflectron for reflecting the ions. In further aspects of the invention, the reflectron can include a front electrode and a back electrode. At least one of the front and back electrodes can be capable of generating a curved electric field. Additionally, the front electrode and back electrodes can be configured to perform time focusing and resolve an image of a specimen.

Abstract: An accumulating ion source for a mass spectrometer that includes a sample injector (328) introducing sample vapors into an ionization space (115) and an electron emitter (102) emitting a continuous electron beam (104) into the ionization space (115) to generate analyte ions. The accumulating ion source further includes first and second electrodes (108a, 108b) arranged spaced apart in the ionization space (115) for accumulating analyte ions substantially therebetween. The first and second electrodes (108a, 108b) receive periodic extraction energy potentials to accelerate packets of analyte ions from the ionization space (115) along a first axis. An orthogonal accelerator (140) receives the packets of analyte ions along the first axis and periodically accelerates the packets of analyte ions along a second axis substantially orthogonal to the first axis.

Abstract: A mass spectrometer is disclosed comprising a MALDI ion source coupled to an orthogonal acceleration Time of Flight mass analyzer. The mass spectrometer is operated at a first instrument setting wherein specific parent ions are selected by a mass filter and are accelerated to a first axial energy. The fragment ions are then orthogonally accelerated after a first delay time and first mass spectral data is obtained. The mass spectrometer is then operated at a second instrument setting wherein the axial energy of the parent ions is increased and the resulting fragment ions are orthogonally accelerated after a reduced delay time. Second mass spectral data is then obtained. The first and second mass spectral data are then combined to provided a final composite mass spectrum.

Abstract: An ion trap mass spectrometer and methods for obtaining a mass spectrum of ions by step scanning the driving frequency in frequency increments over a bandwidth, wherein for each step a specific frequency is held for a fixed number of complete cycles, wherein each specific frequency is changed continuously to the frequency in the next step, and wherein each specific frequency in each step starts at phase zero position.

Abstract: The present invention relates to a device for measuring glow discharge spectrometry in pulsed mode, which includes an RF electric field generator in pulsed mode, a discharge lamp, an impedance matching device for transferring the electric power supplied by the generator to the discharge lamp and a mass spectrometer suitable for measuring at least one signal representative of an ionised plasma species. According to the invention, the device includes a measurement system suitable for measuring a signal representative of the impedance mismatch ?? between the generator and the discharge lamp, said measurement system including a fast acquisition system, synchronized with the pulses and suitable for supplying the impedance matching device with a signal representing the impedance mismatch ?? for at least one part of said pulses. The device enables continuous impedance adaptation.

Abstract: A mass analysis device with wide angular acceptance, notably of the mass spectrometer or atom probe microscope type, includes means for receiving a sample, means for extracting ions from the surface of the sample, and a reflectron producing a torroidal electrostatic field whose equipotential lines are defined by a first curvature in a first direction and a first center of curvature, and a second curvature in a second direction perpendicular to the first direction and a second center of curvature, the sample being positioned close to the first center of curvature.

Abstract: An Atmospheric Pressure Chemical Ionization (APCI) source interfaced to a mass spectrometer is configured with a corona discharge needle positioned inside the APCI inlet probe assembly. Liquid sample flowing into the APCI inlet probe is nebulized and vaporized prior to passing through the corona discharge region all contained in the APCI inlet probe assembly Ions produced in the corona discharge region are focused toward the APCI probe centerline to maximize ion transmission through the APCI probe exit. External electric fields penetrating into the APCI probe exit end opening providing additional centerline focusing of sample ions exiting the APCI probe. The APCI probe is configured to shield the electric field from the corona discharge region while allowing penetration of an external electric field to focus APCI generated ions into an orifice into vacuum for mass to charge analysis.

Abstract: A mass spectrometer with a wide dynamic range, having:—a source (2) of ion beams,—an analyzer (4) for the ion beams generated by said source (2),—a detector (6) for the ions separated by said analyzer (4),—a treatment stage (8) for the analogue signal A generated by said detector, to obtain two separate signals A1=mA and A2=nA, where m>n, characterised by comprising:—an analogue/digital converter (10) for converting both said analogue signals A1 and A2 into two numerical values D1 and D2,—a controller (12) which receives both the numerical values D1 and D2 as input, and provides as output a single value equal to D1 if D1 is less than the end-of-scale value of the converter (10), or a value equal to (m/n)D2 if D1 is equal to the end-of-scale value of the converter.

Abstract: A charged particle spectrum analysis apparatus comprising an electric field generator arranged to subject charged particles to a time-varying electric field, a detector to record charged particle time spectrum data of charged particles which have passed through the electric field, the detector comprising a position-sensitive detection portion, and the time-varying electric field arranged to be activated in synchrony with activation of detector, and the time-varying electric field arranged to subject a predetermined region of said detection portion to consecutive charged particle deflection cycles.

Abstract: A method of reflecting ions in a multireflection time of flight mass spectrometer is disclosed. The method includes guiding ions toward an ion mirror having multiple electrodes, and applying a voltage to the ion mirror electrodes to create an electric field that causes the mean trajectory of the ions to intersect a plane of symmetry of the ion mirror and to exit the ion mirror, wherein the ion are spatially focussed by the mirror to a first location and temporally focused to a second location different from the first location. Apparatus for carrying out the method is also disclosed.

Abstract: Various embodiments of a multi-dimensional ion mobility analyzer are disclosed that have more than one drift chamber and can acquire multi-dimensional ion mobility profiles of substances. The drift chambers of this device can, for example, be operated under independent operational conditions to separate charged particles based on their distinguishable chemical/physical properties. The first dimension drift chamber of this device can be used either as a storage device, a reaction chamber, and/or a drift chamber according to the operational mode of the analyzer. Also presented are various methods of operating an ion mobility spectrometer including, but not limited to, a continuous first dimension ionization methods that can enable ionization of all chemical components in the sample regardless their charge affinity.

Abstract: A system and method for trapping a charged particle is disclosed. A time-varying periodic multipole electric potential is generated in a trapping volume. A charged particle under the influence of the multipole electric field is confined to the trapping volume. A three electrode configuration giving rise to a 3D Paul trap and a four planar electrode configuration giving rise to a 2D Paul trap are disclosed.

Abstract: Time-of-flight mass spectrometer instruments are disclosed for monitoring fast processes with large dynamic range using a multi-threshold TDC data acquisition method or a threshold ADC data acquisition method. Embodiments using a combination of both methods are also disclosed.

Abstract: The present invention concerns a method of detecting the antifungal cyclic hexapeptides Pneumocandin B0 and/or Pneumocandin C0 specific fragment is/are detected using MS in negative mode.

Abstract: A multi-turn time-of-flight mass spectrometer creates, an accurate mass spectrum of a wide mass range, with the smallest number of measurements. Deflecting electrodes are provided on an ejection path through which ions deviating from a loop orbit fly to a detector having two-dimensional array elements. A varying voltage applied to the deflecting electrodes creates an electric field. When two ions having different mass-to-charge ratios simultaneously arrive at the detector, these ions are affected with differing strengths since they pass through the deflecting electric field at different times. This results in arrival for the ions on a detection surface. The time an ion passing through the deflecting electric field can be calculated from the displacement of the arrival position of that ion. Then the flight speed of the ion is obtained and its number of turns is roughly deduced to arrive at its mass-to-charge ratio.

Abstract: In a mass cytometer or mass spectrometer, a sample of elemental tagged particles is transferred from a dispersion to a gas flow through a carrier aerosol spray for atomization and ionization by inductively coupled plasma (ICP) source. The configuration of the sample transfer apparatus allow for total consumption of the sample by passing the sample spray through a deceleration stage to decelerate the spray of particles from its high velocity expansion. Following the deceleration stage, the decelerated sample of particles can be accelerated and focused through an acceleration stage for transferring into the ICP. This effectively improves the particle transfer between the sample spray and the ICP.

Abstract: Described here is a detector for measuring heavy mass ions with high sensitivity and low saturation for time-of-flight mass spectrometry and a detector housing for selecting between multiple detectors.

Abstract: The field of the invention is atmospheric pressure mass spectrometry (MS), and more specifically a process and apparatus which combine infrared laser ablation with electrospray ionization (ESI).

Abstract: Described herein is an ion slicer that: a) accelerates an ion beam towards a first electrode comprising an ion entrance slit, where the first electrode blocks a portion of ions with high displacement from the axis of the ion beam, thereby slicing the ion beam; and then b) decelerates the ion beam after it is sliced.

Abstract: A method and mass spectrometer for filtering ions are provided. The mass spectrometer generally comprises an ion guide, a quadrupole mass filter, a collision cell and a time of flight (ToF) detector, and is enabled to transmit an ion beam through to the ToF detector. The mass spectrometer is operated in MS mode, such that ions in the ion beam remain substantially unfragmented, the quadrupole mass filter operating at a pressure substantially lower than in either of the ion guide and the collision cell. The quadrupole mass filter is operated in a bandpass mode such that ions outside of a range of interest are filtered from the ion beam, leaving ions inside the range of interest in the ion beam. The ions inside the range of interest are analyzed at the ToF detector.

Abstract: The present invention provides an electron spectroscopy apparatus (12) comprising a high energy particle source (12) for irradiating a sample, an electron detector system (16) (e.g. including a delay line detector) for detecting electrons emitted from the sample and an ion gun (8) for delivering a polycyclic aromatic hydrocarbon (PAH) ion beam to the sample, wherein the ion gun comprises a polycyclic aromatic hydrocarbon ion source, for example comprising coronene. In an embodiment, the PAH is located in a heated chamber (22) and vaporised to produce gas phase PAH. The gas phase PAH molecules are then ionised by electron impact, extracted from the ion source via an extraction field and focussed using ion optics. The PAH ion beam can be used for surface cleaning and depth analysis.

Abstract: A mass spectrometer is disclosed comprising a first storage ion trap arranged upstream of a high performance analytical ion trap. According to an embodiment ions are simultaneously scanned from both the first and second ion trap. At any instant in time the quantity of charge present within the second ion trap is limited or restricted so that the second ion trap does not suffer from space charge saturation effects and hence the performance of the second ion trap is not degraded.

Abstract: The present invention is a device to restrict the sampling of analyte ions and neutral molecules from surfaces with mass spectrometry and thereby sample from a defined area or volume. In various embodiments of the present invention, a tube is used to sample ions formed with a defined spatial resolution from desorption ionization at or near atmospheric pressures. In an embodiment of the present invention, electrostatic fields are used to direct ions to either individual tubes or a plurality of tubes positioned in close proximity to the surface of the sample being analyzed. In an embodiment of the present invention, wide diameter sampling tubes can be used in combination with a vacuum inlet to draw ions and neutrals into the spectrometer for analysis. In an embodiment of the present invention, wide diameter sampling tubes in combination with electrostatic fields improve the efficiency of ion collection.

Abstract: A method of mass spectrometry is disclosed wherein a signal output from an ion detector is digitised by an Analogue to Digital Converter and is then deconvoluted to determine one or more ion arrival times and one more ion arrival intensities. The process of deconvoluting the ion signal involves determining a point spread function characteristic of an ion arriving at and being detected by the ion detector. A distribution of ion arrival times which produces a best fit to the digitised signal is then determined given that each ion arrival is assumed to produce a response given by the point spread function. A plurality of ion arrival times are then combined to produce a composite ion arrival time-intensity spectrum.

Abstract: Provided is a time-of-flight mass spectrometer having a reflectron which eliminates energy dependency of the flight time of ions having the same m/z while ensuring a high degree of design freedom. An electric field created by the reflectron is virtually divided into a decelerating region for decelerating ions and a reflecting region for reflecting ions. For an ion having a mass-to-charge ratio which has departed with initial energy higher than Ud, the total flight time required for the ion to travel through a free-flight region and the decelerating region into the reflecting region and return will be equal to the total flight time required for an ion of the same mass-to-charge ratio to make a round trip in which the ion turns around at a point of the reference potential value at the boundary between the decelerating region and the reflecting region or in the decelerating region.

Abstract: A mass spectrometry (MS) method which includes generating in a vicinity of the quadrupole ion trap hydrogen molecules, directing at least part of the hydrogen molecules into the quadrupole ion trap cell, applying AC and DC voltages to quadrupole ion trap cell electrodes to create a combined AC/DC trapping field, placing sample ions inside the quadrupole ion trap cell, cooling at least part of said ions using said hydrogen molecules as a buffer gas, changing the combined AC/DC trapping field to eject the ions from the quadrupole ion trap cell, and detecting the ejected ions.

Abstract: A microtome for in situ residence within a chamber of a scanning electron microscope (SEM) and a SEM including the microtome is disclosed. The microtome includes a specimen holder for holding a specimen thereon at high voltage to produce a retardation field thereat and a movable knife. The SEM includes a backscatter electron detector disposed adjacent to specimen holder. The knife arranged is to be carried into engagement with the specimen on the specimen holder to slice a portion of the specimen away to expose a new face of the specimen without interfering with the high voltage on the specimen, and is mounted so that after having engaged the specimen to expose a new face of the specimen it is withdrawn to a retracted position whereupon it does not interfere with the retardation field.

Abstract: Methods, apparatus and systems for acquiring spectrometric data from analyte ions implement a combination of drift-type ion mobility (IM) separation and time-of-flight mass spectrometry (TOF MS). Both separation techniques are carried out in tandem while applying mass filtering with a wide window of ion isolation. One mode of operation entails utilizing a mass filter to limit ion packets to ions in a selected m/z range that remains constant over the entire course of data acquisition. Another mode entails utilizing the mass filter to limit ion packets to an m/z range that varies over the course of data acquisition.

Abstract: A portable mass spectrometer having an atmospheric pressure interface for introducing ions generated at ambient pressure gas conditions into a vacuum of the mass spectrometer. The mass spectrometer has a vacuum chamber having at least one vacuum section and at least one gas inlet for directing the ambient pressure gas including the ions into the at least one vacuum section. The at least one gas inlet has a gas passage channel of a length L and a limiting cross section S with a ratio of L/S being less than 20,000 cm?1. The mass spectrometer has a radio frequency (RF) ion guide in the at least one vacuum section positioned for collecting the ions from the at least one gas inlet and transmitting the ions further to a mass analyzer for analyzing the ions transmitted from the ion guide.

Abstract: A time-of-flight mass spectrometer includes an ion source that generates ions. A two-field ion accelerator receives the ions generated by the ion source and generates an electric field that accelerates the ions through an ion flight path. A pulsed ion accelerator generates an accelerating electric field that focuses the ions to a focal plane where the ion flight time to the focal plane for an ion of predetermined mass-to-charge ratio is substantially independent to first order of an initial velocity of the ions prior to acceleration. An ion detector is positioned at the focal plane to detect ions. The two-field ion accelerator generates electric fields that cause the ion flight time to the ion detector for an ion of predetermined mass-to-charge ratio to be substantially independent to first order of both the initial position and the initial velocity of the ions prior to acceleration.

Abstract: The present invention relates to a method and apparatus for ionizing a neutral MALDI desorption plume, and in particular, for efficiently measuring the ionized MALDI desorption plume when post-ionization techniques are combined with a medium pressure MALDI-IM-oTOFMS instrument. Additionally, the present disclosure provides a method and apparatus that simultaneously separates tissue-sample MALDI ions by IM-oTOFMS according to their chemical family. After separation, the MALDI ions are directly compared to the ions created by post-ionizing the co-desorbed neutral molecules with a second laser wherein the second laser is delayed by a few hundred microseconds.

Abstract: The invention generally relates to systems and methods for transferring ions for analysis. In certain embodiments, the invention provides a system for analyzing a sample including an ionizing source for converting molecules of a sample into gas phase ions in a region at about atmospheric pressure, an ion analysis device, and an ion transfer member operably coupled to a gas flow generating device, in which the gas flow generating device produces a laminar gas flow that transfers the gas phase ions through the ion transfer member to an inlet of the ion analysis device.

Abstract: An active detector and methods for detecting molecules, including large molecules such as proteins and oligonucleotides, at or near room temperature based on the generation of electrons via field emission (FE) and/or secondary electron emission (SEE). The detector comprises a semiconductor membrane having an external surface that is contacted by one or more molecules, and an internal surface having a thin metallic layer or other type of electron emitting layer. The kinetic energy of molecules contacting the semiconductor membrane is transferred through the membrane and induces the emission of electrons from the emitting layer. An electron detector, which optionally includes means for electron amplification, is positioned to detect the emitted electrons.

Abstract: A mass spectrometer is disclosed wherein an ion signal is split into a first and second signal. The first and second signals are multiplied by different gains and are digitised. Arrival time and intensity pairs are calculated for both digitised signals and the resulting time and intensity pairs are combined to form a high dynamic range spectrum. The spectrum is then combined with other corresponding spectra to form a summed spectrum.

Abstract: A method is used in a time-of-flight mass spectrometer for analysis of a first pulsed ion beam, the ions of which are disposed along the pulse direction, separated with respect to their ion masses. The ions of at least one individual predetermined ion mass or of at least one predetermined range of ion masses can be decoupled from the first pulsed ion beam, as at least one decoupled ion beam, and the first ion beam and the at least one decoupled ion beam are analyzed.

Abstract: An ion-mobility analyser is disclosed comprising a plurality of axially segmented upper electrodes, a plurality of axially segmented lower electrodes, a first plurality of axially segmented intermediate electrodes and a second plurality of axially segmented intermediate electrodes which together define an ion pathway. An asymmetric voltage waveform is applied to the upper electrodes and a DC compensating voltage is applied to the lower electrodes in order to separate ions in a vertical radial direction according to their rate of change of ion mobility with electric field strength. At the same time, a DC axial voltage gradient is maintained along the axial length of the analyser in order to separate ions axially according to their ion mobility.

Abstract: A device for separating ions according to differences in their ion mobility as a function of electric field strength is disclosed. The device comprises an upper electrode, a lower electrode and a plurality of intermediate electrodes. An asymmetric voltage waveform is applied to the upper electrode and a DC compensating voltage is applied to the lower electrode.

Abstract: An ion mobility spectrometer has a pair of electrodes and midway along the drift chamber. A high field is applied between the electrodes and sufficient to modify ions in the region of thee electrodes such that they move at a different rate towards the collector plate. This is used to modify the time of flight of selected ions or ion clusters and enable identification of ambiguous peaks on the IMS spectrum.