The introduction of Circularly Polarized Luminescence by Richardson & Riehl, circa 1977

Remarkably, CPL is only a handful of years younger than CD. But whereas 'everyone' does circular dichroism, only a few laboratories do CPL, both because of the difficulty of making this emissive differential measurement and the unavailability of good commercial instruments. The introduction of the small & affordable CPL Solo in 2019 has expanded use considerably. And according to the pioneers of this measurement, it should be used as widely as circular dichroism. Hear the first page of the 1977 paper here: