235Bi

235Bi is a radioactive isotope of the element bismuth (chemical symbol Bi) with a mass number of 235. It has 83 protons and 152 neutrons. This isotope does not occur naturally and has been produced only in laboratory settings through nuclear reactions, such as neutron irradiation of bismuth targets and various high-energy heavy-ion fusion-evaporation processes.

Because 235Bi lies far from the valley of stability, it is highly unstable and has a very short lifetime. Reported lifetimes are on the order of microseconds to milliseconds, with the exact value depending on how the isotope is produced and its nuclear state. The decay pathways for 235Bi are not fixed and are subject to experimental conditions; possible decay modes include alpha decay and beta decay to lighter nuclei, with branching ratios that vary with energy states and production method.

In the context of nuclear science, 235Bi and other heavy, neutron-rich isotopes are studied to test and refine models of nuclear structure, shell effects, and the limits of nuclear existence near the heaviest elements. Such isotopes help researchers understand how protons and neutrons arrange themselves in very large nuclei and how these nuclei decay when they are far from stability.

See also: isotopes of bismuth; Bi-209, the naturally occurring long-lived isotope of bismuth.