# What's the difference between vibrational relaxation and internal conversion?

According to the following diagram, an excited state can dissipate via vibrational relaxation or internal conversion. Aren't they the same thing?

(source: Barltrop and Coyle, Principles of Photochemistry, 1978)

As an example, imagine a molecule resides in the first excited singlet state, S$_1$($\nu'$) and in vibrational state $\nu'$. It may undergo VET, from state S$_1(\nu')$ $\rightarrow$ S$_1(\nu)$. The heat given out is the energy different between vibrational states $\nu'$ and $\nu$. It may then undergo internal conversion if the vibrational wavefunctions couple electronic states sufficiently strongly cauing an electronic transition, S$_1(\nu)$ $\rightarrow$ S$_0(\nu)$. The molecule is still likely vibrationally excited, and vibrational energy transfer will allow the molecule to return to its ground vibational state (in its ground electronic state).