Past exam of the chemistry A course of the University of Cambridge / 2023 / Paper 1 / A3 / a / ii / Solution

For a transition starting at $J$ and ending at $J+2$, the molecule gainsEnergy conservation therefore gives the scattered-light wavenumbersThe first shifts below the laser are $6\tilde{B},10\tilde{B},14\tilde{B},18\tilde{B}$. Adjacent Stokes lines are separated by $4\tilde{B}$, while the first line is $6\tilde{B}$ from the Rayleigh line. The figure uses positive Raman shift ${\tilde{\nu }}_L-{\tilde{\nu }}_{\mathrm{S}}$; increasing shift means decreasing scattered-light wavenumber.