Time-of-flight
Encyclopedia : T : TI : TIM : Time-of-flight
The Time of flight (TOF) method of measuring particle mass is done as follows. An ion of known electrical charge and unknown mass enters a mass spectrometer and is accelerated by an electrical field of known strength. This acceleration results in any given ion having the same kinetic energy as any other ion given that they all have the same charge. The velocity of the ion will depend however on the mass.
The time that it subsequently takes for the particle to reach a detector at a known distance is measured. This time will depend on the mass of the particle (heavier particles reach lower speeds). From this time and the known experimental parameters one can find the mass of the particle. This method of analysis is a powerful tool for finding the mass of charged particles, atoms and molecules.
In near infrared spectroscopy Time of Flight method is used to estimate the wavelength dependent optical pathlength.
Focusing the ions onto a detector can be accomplished through the use of two or three Einzel lenses placed in the vacuum tube located between the ion source and the detector.
In kinematics, TOF is the duration in which a projectile is travelling through the air. Given the initial velocity [u] of the particle, the downward (ie., gravitational) acceleration [a], and the projectiles angle of projection θ (measured relative to the horizontal), then a simple rearrangement of the suvat equation s=ut+1/2at² results in this equation for the time of flight of a projectile: t=2[u](Sin θ)/[|a|].
External Links
- [ABRF MALDI TOF Tutorial]
- [IFR/JIC TOF MS Tutorial]
- [FAST ComTec TOF Application Note]
- [Jordan TOF Products TOF Mass Spectrometer Tutorial]
- [University of Bristol TOF-MS Tutorial]
References
- Mamyrin, B. A.; Karataev, V. I.; Shmikk, D. V.; Zagulin, V. A. The mass-reflectron, a new nonmagnetic time-of-flight mass spectrometer with high resolution Sov. Phys. JETP, 1973, 37, 45.
- Stephens, W. E., [A Pulsed Mass Spectrometer with Time Dispersion] Phys. Rev., 1946, 69, 691.
- Wiley, W. C.; MacLaren, I. H., [Time-of-Flight Spectrometer with Improved Resolution]Rev. Sci. Instr., 1955, 26, 1150.
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.