Terahertz quantum beats in molecular liquids

With ultrashort pulses of less than 100 fs it is possible to excite
coherently several vibrational modes of polyatomic molecules
simultaneously. The femtosecond time resolution of the experiment
allows the study of pronounced high-frequency beat phenomena up to
10 THz. The frequency difference between vibrational modes
separated by more than 300 cm−1 may be determined with high
precision.