37Cl

37Cl is a stable isotope of chlorine with mass number 37. It has 17 protons and 20 neutrons in its nucleus, and it is one of the two stable isotopes of chlorine, the other being 35Cl.

In nature, 37Cl accounts for about 24.2% of chlorine atoms, while 35Cl makes up about 75.8%. The isotopic masses are approximately 34.9689 u for 35Cl and 36.9659 u for 37Cl, contributing to a standard atomic weight of chlorine of about 35.453.

As a stable isotope, 37Cl does not undergo radioactive decay. Chemically, it behaves very similarly to 35Cl, so most reactions affect both isotopes in the same way. Isotopic fractionation can occur during certain physical or chemical processes, leading to small variations in the 37Cl/35Cl ratio among different materials or reservoirs.

Applications of 37Cl include stable isotope geochemistry and environmental or hydrological tracing. The 37Cl/35Cl ratio is measured to gain information about chlorine sources, cycling, and provenance in rocks, waters, soils, and biological systems. Measurements are typically performed using isotope ratio mass spectrometry (IRMS) or multi-collector ICP-MS, allowing researchers to study processes such as evaporation, water-rock interaction, and contaminant transport through the lens of chlorine isotopes.