Chlorine-37
Chlorine-37, is one of the stable isotopes of chlorine, the other being chlorine-35. Its nucleus contains 17 protons and 20 neutrons for a total of 37 nucleons. Chlorine-37 accounts for 24.22% of natural chlorine, with chlorine-35 the remaining 75.78%, giving chlorine in bulk an apparent atomic weight of.
Remarkably, solar neutrinos were discovered by an experiment using a radiochemical method based on chlorine-37 transmutation.
Neutrino detection
One of the historically important radiochemical methods of solar neutrino detection is based on inverse electron capture triggered by the absorption of an electron neutrino. Chlorine-37 transmutes into argon-37 via the reactionArgon-37 then decays via electron capture into chlorine-37 via the reaction
The detection of these electrons confirms that a neutrino event occurred. Detection methods involve several hundred thousand liters of carbon tetrachloride or tetrachloroethylene stored in underground tanks.