US 3,937,955 AGranted

Fourier transform ion cyclotron resonance spectroscopy method and apparatus

AssigneeNicolet Technology Corporation

InventorsMelvin Barnet Comisarow, Alan George Marshall

Life of this patent

Estimating the term…

Loading patent…

Abstract

A gas sample is introduced into an ion cyclotron resonance cell enclosed in a vacuum chamber, and ionized. A magnetic field constrains ions to circular orbits. After an optional delay adequate to allow ion-molecule reactions to occur, a pulsed broad-band oscillating electric field disposed at right angles to the magnetic field is applied to the ions. As the frequency of the applied electric field reaches the resonant frequency of various ions, those ions absorb energy from the field and accelerate on spiral paths to larger radius orbits. The excited motion is sensed and digitized in the time domain. The result of the digitization is Fourier transformed into the frequency domain for analysis. If desired, a sequential series of pulsed broad-band oscillating fields can be applied and the resulting change in motion sensed, digitized and accumulated in a sequential manner prior to Fourier transformation.

Claims43

Dependent claims

A Fourier transform ion cyclotron resonance mass spectrometer comprising:

an evacuable chamber suitable for receiving a gaseous sample to be mass analyzed;
evacuation means connected to said evacuable chamber for reducing the atmospheric pressure in said chamber to a predetermined level;
an ion cyclotron resonance cell, including a plurality of electrode plates, mounted in said evacuable chamber;
ion forming means for ionizing gases located in said ion cyclotron resonance cell;
magnetic field means for creating a unidirectional magnetic field, said magnetic field means mounted so that said unidirectional magnetic field passes through said ion cyclotron resonance cell in a predetermined direction;
voltage means connected to said plurality of plates of said ion cyclotron resonance cell, said voltage means generating voltages of a level and a polarity adequate to trap substantially all ions of a given charge sign formed by said ion forming means in said ion cyclotron resonance cell, said unidirectional magnetic field means causing said trapped ions to move orbitally at angular frequencies dependent on the mass-to-charge ratio of individual ions;
broad-band excitation means connected to said ion cyclotron resonance cell for producing a broad-band electric field at right angles to said unidirectional magnetic field, said broad-band electric field exciting all ions trapped within said ion cyclotron resonance cell that have a mass-to-charge ratio falling within a predetermined range;
broad-band detection means connected to said ion cyclotron resonance cell for simultaneously detecting the number of ions of each different mass-to-charge ratio excited by said broad-band excitation means and for generating a single time domain analog signal containing information related to the magnitude and nature of said numbers;
digitizing means connected to said broad-band detection means for digitizing said time domain analog signal related to the magnitude and nature of the number of ions of each different mass-to-charge ratio so as to produce a time domain digital signal related to the magnitude and nature of said numbers;
and,
Fourier transform means connected to said digitizing means for transforming said time domain digital signal into a frequency domain signal containing information about the numerical magnitude and frequency of excited ions of each different mass-to-charge ratio trapped in said ion cyclotron resonance cell.

8 more elements

A method of Fourier transform ion cyclotron resonance spectroscopy comprising the steps of:

ionizing a gas sample located within an analyzer cell mounted in an evacuable chamber during an ionizing period;
trapping substantially all ions of a given charge sign formed within the analyzer cell during and after the ionization period and causing them to move obitally at an angular frequency by subjecting them to the combined action of static electric fields and a unidirectional magnetic field;
exciting, during a broad-band ion cyclotron resonance excitation period, all ions trapped within the cell that lie within a range of mass-to-charge ratios by applying a broad-band exciting electric field to said analyzer cell in a direction substantially transverse to the direction of said unidirectional magnetic field;
converting said excited ion cyclotron motion of ions falling within said range of mass-to-charge ratios into a time domain analog signal;
digitizing said analog signal in the time domain to form a time domain digital signal;
and,
converting said time domain digital signal into a frequency domain signal.

4 more elements

Dependencies are inferred from the claim text.