A 532 nm laser Raman spectrometer records $Cl_2$ with fundamental vibration 560 cm$^{-1}$. The Stokes line is observed at ______ cm$^{-1}$ (nearest integer).
The excitation wavenumber is 1/(532×10⁻⁷ cm)=18796.99 cm⁻¹. A Stokes photon loses one vibrational quantum, so subtract the Cl2 vibration: 18796.99−560=18236.99 cm⁻¹. Rounded to the nearest integer the line is **18237 cm⁻¹**. Anti-Stokes scattering would require addition instead.