Krypton
After they are sealed up, krypton and argon gasses are pumped into the space in between.
Krypton has several stable isotopes, the relative abundances of which can be used to parse the gas's source.

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Open the tool →氪气 (kè qì) means “Krypton”.
氪气 is pronounced kè qì in Mandarin Chinese.
“Krypton” is 氪气 (kè qì) in Chinese.
This page has 2 example sentences using 氪气, each with pinyin and an English translation.