Uncertainty relationship for rotational spectroscopy

[jaejoon89]

From uncertainty relationship ∆E τ ~ hbar, what is the lifetime for a state that gives rise to a line of width 0.1 cm^-1? what about for 100 MHz?

How do you get the energy term? I'm really not sure how to do this, would appreciate some insight, thnx.

 

[alxm]

Reciprocal centimeters are a measure of what?

 

[jaejoon89]

So it's the wavenumber...

1) I just use E=hc*(wavenumber), and here E = ∆E?

2) What about for MHz = s^-1 = f
So I just use E = hf?

Or would it be angular frequency and should I use instead E = hbar omega ?