In a triple quadrupole mass spectrometer there are three quadrupoles. A common variation of the transmission quadrupole is the triple quadrupole mass spectrometer. A linear series of three quadrupoles is known as a triple quadrupole mass spectrometer. A changing magnetic quadrupole moment produces electromagnetic radiation. Tandem mass spectrometry that the first and third quadrupole work as a mass filter. The mass spectrometry is typically done by a triple quadrupole MS. Atomic nuclei with spin formula 26 have an electric quadrupole moment. This corresponds to the traceless electric quadrupole moment tensor formula 75. The measured electric quadrupole of the deuterium is . This is an alternative method to the use of nuclear quadrupole resonance spectroscopy. Thermo Fisher's LTQ ("linear trap quadrupole") is an example of the linear ion trap. Ions travel down the quadrupole between the rods. An example of a magnetic quadrupole, involving permanent magnets, is depicted on the right. When analytes pass the second quadrupole, the fragmentation proceeds through collision with gas. This gives it a nonzero quadrupole moment.