July 2018

Sulfur Monoxide
Cation

Singly ionized sulfur monoxide (SO+) was detected by Turner in 1992 in the "shocked molecular clump" IC 443G. The observations were made with the NRAO 12m radio telescope. Turner suggested that SO+ was evidence for shock chemistry, that it was formed via a dissociative shock. However, van Dishoeck et al. countered that SO+ could be formed without a shock, if S+ is present in pre-shocked gas.

Researcher Links
Turner 1992
Muller et al 2009

SO+ has also been detected toward the quasar PKS 1830-211, as reported by Muller et al in 2011. See Holger Müller's entry on extragalactic SO+ for more details about the detection.

When SO is ionized, the electron is removed from the sulfur 3p2 orbital, leaving a phosphorus-like 3s2 3px 3py 3pz configuration. That means that when O bonds to it, there is one σ bond and one π bond, with one singly occupied orbital leftover on sulfur. There are two ways to do this, as shown below in the bonding diagrams below. SO+ has a 2Π ground state, which gives it distictively doubled lines. The doubly and singly occupied valence π orbitals are also shown.


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