Ground state vibrational wave‐packet and recovery dynamics studied by time‐resolved CARS and pump‐CARS spectroscopy

Recent experiments on gaseous iodine and β‐carotene are analyzed within a wave‐packet description of femtosecond‐time resolved four‐wave mixing spectroscopy. Employing the same formalism, two different experimental setups, both established in the Kiefer group, are treated. In a transient four‐wave‐mixing (FWM) experiment, where two pulses interact simultaneously with the system, the interaction with a third time‐delayed pulse leads to light emission reflecting ground state vibrational dynamics in I2. On the other hand, delaying a FWM‐pulse sequence with respect to a single pump pulse interacting with β‐carotene yields a signal that is directly proportional to the population of a selected nuclear eigenstate in the electronic ground state. Thus, within this setup, it is possible to monitor ground‐state re‐population dynamics mode specifically.