Comment by mycall

Interesting how "through a process called singlet exciton fission" and other article "General Formula for Bi-Aspheric Singlet Lens Design Free of Spherical Aberration" [1] both deal with Singlets. Odd coincidence of the day.

[1] https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-31-9...