Resolving the electron temperature discrepancies in H II regions and planetary nebulae: kappa-distributed electrons by David C. Nicholls and others Created 2026-10-20 Updated 2026-11-05
By David C. Nicholls, Michael A. Dopita and Ralph S. Sutherland. arXiv:1204.3880v2 (2012). Section 4, equation 18 and the following paragraph give a low-density Maxwellian oxygen-line approximation and its collision-strength qualification.