How do you calculate mass of an atom using mass spectrometer?

Answer 1

you can measure the speed by timing time-of-flight, you know the charge on the (ionized) atom, you know the strength of the magnetic field. You measure the radius of curvature in the magnetic field which gives you the mass

Answer 2

atoms are excited,

electrons jump to other shells and their own shells forth and through,

so electromagnetic waves (light) come out of the atoms,

which is different for different substance,

the spectroscope measures the pattern of it and thus calculates Atomic Mass

Answer 3

First off, there are several types of mass spectrometers but in general, there are only two major methods of detection. In ion trap and time of flight (TOF) mass analyzers, electron multipliers or multichannel plates (essentially an array of electron multipliers) are used. These can either be used directly or in conjunction with a conversion dynode. In operation, as ions are mass selectively ejected from an ion trap or arrive at the detector of a TOF, they are accelerated through a large potential (15 kV or so) to a conversion dynode. The ions then impact the dynode and generate secondary electrons and negative ions (in the case of positive ions (I will stick with positive ions for the rest of this discussion)). These negatively charge particles then impinge upon the electron multiplier. Electron multipliers use a resistive film or a series of discrete electrodes to amplify signals. As each negative particle collides with the surface of the electron multiplier, more electrons are released from the surface. This process repeats until the current generated reaches an anode and is ultimately detected via an electrometer that reads the signal as a voltage. In typical operation, electron multipliers provide gains of around 40,000, meaning that for every electron that enters the device, 40,000 electrons result. Thus, abundance is related to the signal detected via the gain of the electron multipliers and the number of charges that initially struck the conversion dynode following mass selective ejection.

The other major detection scheme is based on image current. In certain types of mass spectrometers, ions are forced to move in such a way that the frequency of their motion is directly related to their mass to charge ratio. As they undergo these periodic oscillations, they move past conductive electrodes. Since the particles are charged, they draw electrons (in the case of positive ions) or electron holes (in the case of negative ions) to the conductive electrode to which they are nearest. Thus, if one uses two electrodes that are electrically connected, an image current may be seen passing back and forth between the electrodes as the ions approach the electrodes sequentially during their oscillatory motion. This image current, when detected, provides a sine wave whose amplitude is directly related to the number of charges in the packet of ions inducing the current and whose frequency is related to the mass to charge ratio of the ions that comprise the packet of ions inducing the current. A Fourier transform of this sine wave shifts it from the time domain to the frequency domain and results in a mass spectra where the x-axis corresponds to mass to charge ratio (or frequency) and y- axis is amplitude. In the case of FT instruments, the amplitude is again related to the number of charges in a packet of ions undergoing oscillatory motion and inducing an image current. Typically, before the signal is detected, it is amplified. However, amplification of the signal is limited to gains of 1-4,000. This fundamental difference in image current detection from electron multiplier based detection methods result in FT instruments being less sensitive than ion trap instruments (in general).

Answer 4

in modern instrument,each ion strikes a detector,ionic current is amplified and is fed to the recorder. The recorder makes a graph showing the relative abundance

Answer 5

By the height of the peak due to that ion.