Transient terahertz absorption spectroscopy and suppression of the NLO response of merocyanine derivatives of malonodinitriles

Excitation and relaxation dynamics of low frequency vibrational modes have been studied in the series of merocyanines - derivatives of malonodinitrile using optical pump-terahertz probe spectroscopy. The transient absorption spectra of the merocyanine derivatives exhibit specific features that were analysed in the context of molecular and electronic structural changes. For the first time we can explain the suppression of the nonlinear optical (NLO) response due to the excitation of the vibrations in the THz frequency range.