The charge excitation in the Raman process as correlated from a classical theory for Raman optical activity: The case study of (+)-(R)-methyloxirane

► We developed a classical algorithm to calculate the spectral signs. ► The ROA spectral signs of (+)-(R)-methyloxirane were analyzed by this approach. ► The charges due to the Raman excitation are associated with bond polarizabilities. ► Around 20% of the electrons in the molecule are excited in the Raman process.