Comparison of Surface‐Enhanced Raman and Hyper‐Raman Spectra of the Triphenylmethane Dyes Crystal Violet and Malachite Green

Vibrational spectra of two dyes, malachite green and crystal violet are presented. Raman and hyper‐Raman spectra are recorded as surface‐enhanced (hyper‐) Raman spectra on silver colloids. These data are compared to the respective IR spectra with respect to the point group of the molecules (C2 and C3). Theoretical calculations (PM3 semiempirical) and polarized Raman spectra are used to give an assignment of some vibrational bands. The advantage of SERS (surface‐enhanced Raman scattering) and SEHRS (surface‐enhanced hyper‐Raman scattering) is discussed for the analysis of vibrational spectra.