When was the reduced planck constant $\hbar= h/2\pi$ first introduced and what was the reason behind introducing such a constant?
I know that $E=\hbar \omega$ and $p=\hbar k$ and writing again and again the $2\pi$ in $E=(h/2\pi)\omega$ $p=(h/2\pi) k$ etc. must really annoy the physicist of the time. However there are alternatives to these quantities namely $E=h \nu$ and $p=h/\lambda$. What was the reason preferring $\omega$ and $k$ over $\nu$ and $\lambda$ at the cost of introducing a new constant