Probing Ultrafast Internal Conversion in Ethylene Using Vacuum Ultraviolet Pulses*

Molecules with the ability to quickly dissipate energy when exposed to light play a fundamental role in processes such as vision and DNA photostability. The motion that these large molecules execute to achieve radiationless de-excitation is often centered about a single carbon-carbon double bond. Ethylene is the smallest molecule with a carbon-carbon double bond, and exhibits internal conversion within 50 to 100 femtoseconds of excitation. Using intense vacuum ultraviolet (VUV) light produced from a high harmonics source, we perform pump-probe spectroscopy on ethylene with both arms containing VUV light. By collecting both photoelectrons and photoions, we can gain new insight into the time evolution of ethylene's excited state.