Why is the Caesium 133 atom used in atomic clocks?

When you put all the possible candidate elements against this table, you find that Cs-133 is your top candidate. ... It's worth noting that your statement "Modern atomic clocks only use caesium atoms" is simply untrue. At the very ... So if the second is defined by caesium, why did I say that not all clocks use it? read more

Caesium-based atomic clocks use the electromagnetic transitions in the hyperfine structure of caesium-133 atoms as a reference point. This is because under excitation of microwaves the oscillations resulting from the transition in the hyperfine structure of the Caesium 133 atom take place at exactly 9,192, 631,770 per second. read more