For you I would recommend ħ (pronounced h-hat or h-bar). The constant ħ is the reduced Planck constant, [h / (2π)]. It's equal to 6.582119514(40)×10−16 eV-sec. Don't confuse it (on your freaking life) for Ĥ, which is the Hamiltonian Operator corresponding to the total energy of a system.