Tellurium (Te) in plasma
Tellurium makes the widest ring here, a thick pale band rather than a cord, and it is edged in green where it meets the core. That edge is tellurium itself: its two brightest neutral lines sit at 508 and 515 nm, both squarely green, while the white body of the ring is mostly the buffer gas. The dark middle goes teal instead of the usual near-black. Two frames are a different vessel, where the same fill turns pink and throws filaments at the glass instead of closing a ring.
Tellurium color is very hard to catch, as it tends to form a film on the inner wall of the flask, which ruins the bagel upon heating, and remains idle otherwise.
