The Planck Constant (h) is 6.626068 × 10-34 m2 kg/s. The relation of a photon's energy to frequency is
E = h × f
(E being energy, f being Frequency).
The Reduced Planck Constant (or Dirac Constant, abbreviated ℏ) is h/2π, which is convenient because many equations incorporate this expression.
Carbon Monoxide (CO)
Stefan-Boltzmann Constant (σ)