Exploring vibrational coherence of molecular systems with simultaneous excitation of close frequencies using the CLIO-FEL

We studied the vibrational coherence of DCl molecules and clusters embedded in solid nitrogen by means of photon echo experiments using the CLIO-FEL. Infrared vibrational spectra of the samples exhibit numerous absorption bands assigned to different species in the 2080–2020 wavenumber range. The tunability of the laser source in terms of spectral range, spectral width of the IR pulses allows to excite coherently these species in different ways. The time-resolved non-linear response of the sample depends on the various experimental conditions. We observe various time features, involving oscillations related to the number of simultaneously excited vibrational modes, and time decays related to the average coherence time of the probed transitions. All these results bring a complete information on vibrational dynamics of the different trapped species.