Conventional laser systems have laser pulse durations of around one nanosecond or longer which does not allow us to directly observe internal conversion processes. Using the spectra physics ultrafast oscillator and amplifier systems we can generate ~ 150fs laser pulses in the UV and IR for pump-probe spectroscopic measurements on molecules exhibiting fast internal conversion. The figure shows the experimental setup where both UV and IR lasers start from an ultrafast Ti : Sapphire amplifier, a 40:60 beam splitter creates two beams one 800nm that is sent into a delay stage and another goes through a third harmonic generator to create 267nm and then to the spectrometer.
Using resonance enhanced multi-photon ionization where the pump (267nm) laser excites an electronic state and the probe laser ionizes the molecules still in the excited state but not in the ground state. The delay will give us the excited state lifetimes of these molecules by the ionization vs delay time.