radiation constants in spectrochemistry

https://dx.doi.org/10.1351/goldbook.R05051
Fundamental physical constants characterizing black body radiation. The first radiation constant is c 1 = 2 π h c 0 2 = 3.741 7749 22 × 10 −16 W m 2, the second is c 2 = h c 0 k = 1.438 769 12 × 10 −2 m K, where h is the Planck constantc 0 the speed of light and k the Boltzmann constant.
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