The primed $f'_{\rm TS}$ is the corresponding <transition state> <partition function> per unit <volume> with the unstable reaction-coordinate degree of freedom omitted. Its replacement by the crossing-frequency factor $kT/h$ is already outside the partition-function ratio. For a diatomic atom-pair transition state, the omitted coordinate is the bond stretch, leaving translation and rotation.

Solution

Past exam of the chemistry A course of the University of Cambridge / 2025 / Paper 2 / A8 / b / ii / Solution

 Solution (source code)