Femtosecond laser-controlled selective excitation of vibrational modes on a multidimensional ground state potential energy surface

In this Letter, we report the controlled selective excitation of vibrationa l modes in the electronic ground state of polymers of diacetylene. The tech nique applied for exciting and probing is femtosecond time-resolved four-wa ve mixing spectroscopy with broad-band detection. We use a coherent anti-St okes Raman scheme, where the difference of pump and Stokes laser wavelength s is chosen to achieve resonance with several chain modes of the polydiacet ylenes. By varying the timing and the phases of the femtosecond laser pulse s, the timing and intensity of these modes can be strongly influenced. (C) 2000 Elsevier Science B.V. All rights reserved.