Isotope Ratio Mass Spectrometers (IRMS) Ionization ►Make the Ions Deflection ►Separate the Ions Detection ►Count the Ions

Isotope Ratio Mass Spectrometers (IRMS) Next, the ions are accelerated toward an electromagnet through the flight tube. The electromagnet deflects the ions. Electromagnet Flight Tube Gas Ion+ Ion Source First, gas molecules are turned into ions in the ion source. 1H2 ‘Light’ ions are deflected further than ‘heavy’ ions. DH lighter ions heavier ions Carbon Dioxide (CO2) 12C16O2 M (mass 44) 13C16O2 M+1 (mass 45) 12C18O16O M+2 (mass 46) Carbon Dioxide (CO2) 12C16O2 M (mass 44) 13C16O2 M+1 (mass 45) 12C17O16O M+1 (mass 45) 12C18O16O M+2 (mass 46) M+2 M+1 M Finally, detectors count the number of ions for each mass. Detectors

Ionization – Electron Impact Source Electron Trap Magnet compresses electron beam N S Electrostatic Lenses e e Gas Inlet e Ionization Efficiency 1 ion / 1000 gas molecules Gas Ion+ Ion+ Ion+ Ionization Chamber e e e e e e e Magnet compresses electron beam N S Cathode Extraction X-Focus Slit X-Deflection Y-Deflection Electron Source Form Ion Beam Focus Ions on the Slit Guide Ions Toward Detectors.

Take a Deep Breath… Here Comes Some Heavy Lifting

Ion Deflection: The Math Ions are ejected from the ion source by an accelerating electric field (V) Ep = zV = 1/2 mv2 = Ek Ep = potential energy Ek = kinetic energy m = ion mass z = ion charge V = electric field potential v = ion velocity As the ions pass through magnetic field (B) the ions are forced to follow a circular path of radius (r) (Lorentz force law). Fc = mv2/r = zvB = FB Fc = centripetal force FB = magnetic force m B2 2V z = Ion Mass Acceleration Potential Magnetic Field Ion Charge Radius r2 Ion Source Electromagnet z m = k r2 Solving for v: v = [2zV/m]1/2 This equation shows that if B and V are held constant, ions of different mass-to-charge (m/z) will follow circular pathways of different radii (r) Combine the two equations Solving for v: v = zrB/m

m z Ion Deflection: Electromagnet (The Right Hand Rule – Positive Charge) v F v B (out of screen) Magnetic Field (B) (coming out of the screen) Heavy Ion v F B Velocity Vector (v) Force (F) Magnetic Vector (B) Light Ion F z m = k r2 F F Note: Force F is perpendicular to both the velocity vector (v) and the magnetic field vector (B).

Ion Detection: Faraday Cup Array Mass+2 Mass Mass+1 ion beam ion beam Cup 4 ion beam Cup 3 Cup 2

Ion Detection: Faraday Cup Collector Slit Faraday Cup Ion Count + _ Ion+ Ion+ Ion+ e- e- e- e- Ion+ 1 2 3 4 Ion Beam Electron Source Ground Secondary Electron Suppression Shield

Isotope Ratio Infrared Spectroscopy (IRIS) Bend ► Lasers and Mirrors Symmetric Stretch Asymmetric Stretch

Isotope Ratio Infrared Spectroscopy (IRIS) Infrared Absorption Spectra of 12C16O2 Mid-infrared absorption lines of a subset of the isotopologues of CO2. Waechter 2007

Isotope Ratio Infrared Spectroscopy (IRIS) Tunable Diode Laser H2O H2O Mirror H2O H2O Syringe Mirror H2O H2O H2O H2O H2O H2O H2O Water Photodetector Sample Inlet Sample Outlet 100 Time H2O Empty % H2O Vaporizer