Planck constant

https://doi.org/10.1351/goldbook.P04685
Universal fundamental physical constant h = 6.6260689633 x 10E-34 J s, or ℏ = h2π = 1.05457162853 x 10E-34 J s. The latter is used as atomic unit of action.
Source:
CODATA Bull. 1986, 63, 1 (https://doi.org/10.6028/jres.092.010)