Helium
氦
Helium is the lightest noble gas with two electrons filling the 1s state to close the first shell. It is the second most abundant element in the universe, following hydrogen.
The hydrogen-helium abundance ratio is an important clue to the cosmological process.
氦是最轻的惰性气体，其两个电子填满1s态以闭合第一电子壳层。它是宇宙中第二丰富的元素，仅次于氢。氢和氦的丰度比是宇宙学过程的重要线索。
On the earth, helium is not abundant, being found only in very small quantities in the earth's atmosphere. It was in fact discovered in the sun by the helium spectrum in 1868, long before it was discovered on the earth.
在接地状态下，氦并不丰富，仅在地球大气中以极少量存在。事实上，氦是在1868年通过太阳的氦谱线发现的，比在地球上发现得要早很多。
Helium occurs as a gas entrapped in some uranium minerals, from which it can be liberated by heating. This helium presumably has its origin from alpha decay in the radioactive material. Helium is also present in natural gas from some wells, especially in Texas and Canada, and this is its principal source.
氦气存在于某些铀矿物中，加热后可以释放出这种气体。这种氦气很可能来源于放射性物质中的α衰变。此外，氦也存在于一些天然气田中，尤其是在得克萨斯州和加拿大，这是其主要来源。
Helium is used for filling balloons and dirigibles. It is mixed with oxygen (heliox) for breathing by deep ocean divers to avoid the "bends" from the nitrogen content of the breathed air.
氦用于充填气球和飞艇。它与氧气混合（氦氧混合气）供深海潜水员呼吸，以避免呼吸空气中氮气含量导致的“减压病”。
Liquid helium provides the most practical way to achieve temperatures below 20K for research purposes, and it provides the coolant for achieving superconductivity with the Type I superconductors.
液氦是实现低于20K温度以进行研究的最实用方法，它也是实现I型超导体超导性的冷却剂。
For high vacuum research, helium provides a sensitive way to locate leaks in the vacuum system. A helium mass spectrometer is attached to the vacuum system and then a small jet of helium is released outside the vacuum at locations where leaks are suspected. The detection of helium by the mass spectrometer shows that some is getting into the system, and that the release must be close to the leak.
对于高真空研究，氦气提供了一种灵敏的方法来检测真空系统的泄漏。一个质谱仪被连接到真空系统上，然后在怀疑有泄漏的位置释放一小股氦气。质谱仪检测到氦气的存在，表明有些气体进入了系统，且释放点必须接近泄漏点。
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