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caesium

British  
/ ˈsiːzɪəm /

noun

  1. a ductile silvery-white element of the alkali metal group that is the most electropositive metal. It occurs in pollucite and lepidolite and is used in photocells. The radioisotope caesium-137 , with a half-life of 30.2 years, is used in radiotherapy. Symbol: Cs; atomic no: 55; atomic wt: 132.90543; valency: 1; relative density: 1.873; melting pt: 28.39±0.01°C; boiling pt: 671°C

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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Within the sensors, the light passes through a small glass container containing a caesium gas, which absorbs the light at the right light frequencies.

From Science Daily May 2, 2024

The small silver cylinder is a 19-becquerel caesium 137 ceramic source commonly used in radiation gauges.

From Seattle Times Jan. 28, 2023

The radioactive strontium, caesium and plutonium mainly affected Ukraine and neighboring Belarus, as well as parts of Russia and Europe.

From Reuters Feb. 25, 2022

Previous state-of-the-art caesium clocks are based on measuring microwaves emitted as the atoms transition between two energy states—a process triggered by dropping clouds of atoms and bombarding them with microwaves.

From Scientific American Sep. 9, 2021

Rubidium, caesium, thallium, indium and gallium were first discovered by means of this instrument; the study of the rare earths is greatly facilitated, and the composition of the heavenly bodies alone determinable by it.

From Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 1 "Châtelet" to "Chicago" by Various

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