The simple diatomic radical carbon monosulphide
(CP) was detected in
the circumstellar envelope of IRC+10216 by
Guélin et al.
and reported in 1990. The identification was made by matching 10 rotational lines
observed with the
IRAM 30m radio telescope.
CP and CN are
pnictogenic cousins of the
CO, respectively. Aside from differences in the
masses of the heavy atoms in each diatomic, CP and CN are both open-shell species with doublet Π ground electronic
states, while the ground states of CS and CO are closed-shell.