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Unlike the helium hydride ion, the neutral helium hydride molecule HeH is not stable in the ground state. However, it does exist in an excited state as an excimer (HeH*), and its spectrum was first observed in the mid-1980s. [19] [20] [21] The neutral molecule is the first entry in the Gmelin database. [4]
The helium hydride ion, thought to be the earliest molecule to have been formed in the Universe (about 100,000 years after the Big Bang), was detected in 2019 for the first time in space in NGC 7027. [21] [22] There is also evidence for the presence of nanodiamond in NGC 7027. [23]
It was the first known triatomic helium van der Waals molecule. It can be detected by fluorescence. HeI 2 has a similar optical spectrum to I 2, except that the bands and lines are shifted to form two extra series. One series is blueshifted by between 2.4 and 4.0 cm −1, and the other between 9.4 and 9.9 cm −1. The two series may be due to ...
In April 2019, this molecule was first announced to have been observed in interstellar space, in NGC 7027, a planetary nebula within this galaxy. [58] Much later, atomic hydrogen reacted with helium hydride to create molecular hydrogen, the fuel required for star formation .
The first molecule detected in the interstellar medium was the methylidyne radical (CH •) in 1937, through its strong electronic transition at 4300 angstroms (in the optical). [4] Advances in astronomical instrumentation have led to increasing numbers of new detections.
Whereas the carbon–helium-ion bond breaks spontaneously and immediately to yield a carbocation, bonds of other elements to helium are more stable. For example, molecular tritium T 2 or tritium-hydrogen HT. On decay, these form a stable helium hydride ion [HeH] + (respectively [3 HeT] + or [3 HeH] +), which is stable enough to persist. This ...
Helium also has a very low boiling point (-268.9°C or -452°F), allowing it to remain a gas even in super-cold environments, an important feature because many rocket fuels are stored in that ...
Argonium (also called the argon hydride cation, the hydridoargon(1+) ion, or protonated argon; chemical formula ArH +) is a cation combining a proton and an argon atom. It can be made in an electric discharge , and was the first noble gas molecular ion to be found in interstellar space.