Picosecond pump-probe using an FEL and synchrotron source

Two color pump-probe experiments using the Duke Storage Ring as a synchrotron light source for visible light and the Mark III FEL as a tunable, high peak power IR source are possible. The storage ring RF booster and the Mark III FEL RF sources are both driven by the same master oscillator with a timing jitter between sources of less than 20 psec. The operation of the Mark III FEL results in a pulse structure of 2 psec pulses separated by 350 psec contained in a macropulse of 2 μsec duration which is repeated at 10 - 30 Hz. The storage ring can fill from 1 - 64 RF bunches, each with a synchrotron light pulse length of 20 - 30 psec. The circulator frequency for a single bunch is 2.79 MHz. Synchronized operation will result in a coincidence of 6 FEL-IR pulses with the visible synchrotron pulses for each 2 μsec macropulse, or multiples of 6 for multiple bunches in the ring. The visible synchrotron source can be used as a probe of vibrational excitation from the FEL in an experiment using vibrationally-assisted fluorescence as an indicator of overlap of the IR and the visible pulses. An optical delay line in the FEL beam will allow adjustment of the arrival time of the IR pulse relative to the visible probe. Exploration of coupling between electronic excitation and lifetimes of vibrational excitation of fluorescent compounds in solution can be carried out with this configuration.