Name, symbol Chlorine-36,36Cl
Neutrons 19
Protons 17
Nuclide data
Natural abundance 7 × 10-13
Half-life 301,000 ± 4,000 years

Chlorine-36 is an isotope of chlorine. Chlorine has two stable isotopes and one radioactive environmental isotope: the cosmogenic isotope 36Cl. The ratio of 36Cl to stable 37Cl in the environment is ~700 × 10−15. Its half-life is 301,000 ± 4,000 years. The long half-life of 36Cl makes it useful to date groundwater up to one million years old.[1] There also are observed natural variations in 37Cl. Most such variations in 37Cl values of hydrologic systems are related to diffusion processes.

Chlorine-36 is produced in the upper atmosphere through spallation reactions and in solid materials on the surface of the earth in three ways: spallation reactions, muon reactions and thermal neutron absorption. Spallation reactions also occur when gamma rays interact with minerals in the top several meters of the Earth's surface. It can also be produced through muon reactions and thermal neutron absorption. 36Cl was also produced during nuclear bomb testing in the middle of the 20th century.

Trace amounts of radioactive 36Cl exist in the environment, in a ratio of about 7 × 10−13 to 1 with stable isotopes. 36Cl is produced in the atmosphere by spallation of 36Ar by interactions with cosmic ray protons. In the subsurface environment, 36Cl is generated primarily as a result of neutron capture by 35Cl or muon capture by 40Ca. 36Cl decays to 36S and to 36Ar, with a combined half-life of 308,000 years. The half-life of this hydrophilic nonreactive isotope makes it suitable for geologic dating in the range of 60,000 to 1 million years. Additionally, large amounts of 36Cl were produced by irradiation of seawater during atmospheric detonations of nuclear weapons between 1952 and 1958. The residence time of 36Cl in the atmosphere is about 2 years. Thus, as an event marker of 1950s water in soil and ground water, 36Cl is also useful for dating waters less than 50 years before the present. 36Cl has seen use in other areas of the geological sciences, including dating ice and sediments.

Decay-rate fluctuations

There have been recent reports (2010) identifying fluctuations in the detection rates from 36Cl and other isotopes.[2] At the time of writing it has not been determined if these represent genuine anomalies in the decay rate or have some more mundane explanation.

See also


  1. ^ "Chlorine". Isotopes & Hydrology. 
  2. ^ D. Javorsek II et al. (2010). "Power Spectrum Analyses of Nuclear Decay Rates". Astroparticle Physics 34: 173. arXiv:1007.0924. Bibcode 2010APh....34..173J. doi:10.1016/j.astropartphys.2010.06.011. 

Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Chlorine-37 — Full table General Name, symbol Chlorine 37,37Cl Neutrons 20 Protons 17 …   Wikipedia

  • Chlorine — Chlo rine, n. [Gr. ? pale green, greenish yellow. So named from its color. See {Yellow}.] (Chem.) One of the elementary substances, commonly isolated as a greenish yellow gas, two and one half times as heavy as air, of an intensely disagreeable… …   The Collaborative International Dictionary of English

  • Chlorine — (Chem.), so v. w. Chlor …   Pierer's Universal-Lexikon

  • Chlorīne — Chlorīne, veralteter Name des Chlors; s. auch Resorcin …   Meyers Großes Konversations-Lexikon

  • chlorine — Symbol: Cl Atomic number: 17 Atomic weight: 35.453 Halogen element. Poisonous greenish yellow gas. Occurs widely in nature as sodium chloride in seawater. Reacts directly with many elements and compounds, strong oxidizing agent. Discovered by… …   Elements of periodic system

  • chlorine — nonmetallic element, coined 1810 by English chemist Sir Humphry Davy (1778 1829) from Gk. khloros pale green (see CHLOE (Cf. Chloe)) + chemical suffix INE (Cf. ine) (2). Named for its color. Discovered 1774, but known at first as oxymuriatic acid …   Etymology dictionary

  • chlorine — ► NOUN ▪ a poisonous, irritant, pale green gaseous chemical element. ORIGIN from Greek khl ros green …   English terms dictionary

  • chlorine — [klôr′ēn΄, klôr′in] n. [< Gr chlōros, pale green (< IE * ghlō , var. of base * ghel : see YELLOW) + INE3: so named (1810) by DAVY Sir Humphry, who proved it to be an element, for its color] a greenish yellow, poisonous, gaseous chemical… …   English World dictionary

  • Chlorine — This article is about the chemical element. For the bleach, see Sodium hypochlorite. For the upcoming film, see Chlorine (film). sulfur ← chlorine → argon F ↑ Cl ↓ Br …   Wikipedia

  • chlorine — chlorinous, adj. /klawr een, in, klohr /, n. a halogen element, a heavy, greenish yellow, incombustible, water soluble, poisonous gas that is highly irritating to the respiratory organs, obtained chiefly by electrolysis of sodium chloride brine:… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”