Infrared spectrum of H +3 as an astronomical probe

Abstract

According to the current theory of interstellar chemistry advanced in the early 1970s, the protonated hydrogen molecular ion H⁺₃ plays the crucial role in initiating a chain of ion–neutral reactions. The infrared spectrum of H⁺₃ was first observed in the laboratory in 1980 and has been extended greatly since. The spectrum has been observed as intense emission in polar regions of Jupiter, and very recently in Uranus and Saturn. Its detection has also been claimed in Supernova 1987A, and intense searching for the spectrum in interstellar space is in progress. We summarize the laboratory observation of the H⁺₃ spectrum and its use as an astronomical probe.